Restore macOS CI execution with merge commits

This PR partially reverts elastic#39533 and restores the execution of macOS CI
with merge commits (`main` + release branches) since there is coverage
via GH actions.

It also removes the GH actions to avoid duplicate checks.

.buildkite/auditbeat/auditbeat-pipeline.yml

@@ -194,7 +194,7 @@ steps:
               context: "auditbeat: Linux arm64 Unit Tests"
 
       - label: ":mac: Auditbeat macOS x86_64 Unit Tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh
@@ -214,7 +214,7 @@ steps:
               context: "auditbeat: macOS x86_64 Unit Tests"
 
       - label: ":mac: Auditbeat macOS arm64 ARM Unit Tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh

.buildkite/filebeat/filebeat-pipeline.yml

@@ -133,7 +133,7 @@ steps:
     steps:
       - label: ":mac: Filebeat macOS x86_64 Unit Tests"
         key: "macos-unit-tests-extended"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh
@@ -154,7 +154,7 @@ steps:
 
       - label: ":mac: Filebeat macOS arm64 Unit Tests"
         key: "macos-arm64-unit-tests-extended"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh

.buildkite/heartbeat/heartbeat-pipeline.yml

@@ -166,7 +166,7 @@ steps:
 
   - group: "Heartbeat Extended Testing MacOS"
     key: "heartbeat-extended-tests-macos"
-    if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+    if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
     steps:
       - label: ":mac: Heartbeat MacOS Unit Tests"
         key: "macos-extended"

.buildkite/metricbeat/pipeline.yml

@@ -244,7 +244,7 @@ steps:
 
   - group: "Metricbeat Extended MacOS Tests"
     key: "metricbeat-extended-macos-tests"
-    if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+    if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
     steps:
       - label: ":mac: MacOS x64_64 Unit Tests"
         key: "extended-macos-x64-64-unit-tests"

.buildkite/packetbeat/pipeline.packetbeat.yml

@@ -175,7 +175,7 @@ steps:
     steps:
       - label: ":mac: MacOS x86_64 Unit Tests"
         key: "macos-x86-64-unit-tests-extended"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh

.buildkite/x-pack/pipeline.xpack.auditbeat.yml

@@ -184,7 +184,7 @@ steps:
 
   - group: "x-pack/auditbeat MacOS Extended Tests"
     key: "x-pack-auditbeat-extended-tests-macos"
-    if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+    if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
     steps:
       - label: ":mac: MacOS x86_64 Unit Tests"
         command: |

.buildkite/x-pack/pipeline.xpack.filebeat.yml

@@ -226,7 +226,7 @@ steps:
     key: "x-pack-filebeat-extended-tests"
     steps:
       - label: ":mac: MacOS x86_64 Unit Tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*(macOS).*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh
@@ -246,7 +246,7 @@ steps:
 
       - label: ":mac: MacOS arm64 Unit Tests"
         skip: "https://github.com/elastic/beats/issues/33036"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*(macOS).*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh

.buildkite/x-pack/pipeline.xpack.heartbeat.yml

@@ -197,7 +197,7 @@ steps:
 
   - group: "x-pack/heartbeat macOS Extended Tests"
     key: "x-pack-heartbeat-extended-tests-macos"
-    if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+    if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
 
     steps:
       - label: ":mac: x-pack/heartbeat macOS x86_64 Unit Tests"

.buildkite/x-pack/pipeline.xpack.metricbeat.yml

@@ -208,7 +208,7 @@ steps:
     if: build.env("BUILDKITE_PULL_REQUEST") == "false"  || build.env("GITHUB_PR_LABELS") =~ /.*(macOS|aws).*/
     steps:
       - label: ":mac: MacOS x86_64 Unit Tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.**/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh
@@ -228,7 +228,7 @@ steps:
 
       - label: ":mac: MacOS arm64 Unit Tests"
         skip: "https://github.com/elastic/beats/issues/33036"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.**/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
         command: |
           set -euo pipefail
           source .buildkite/scripts/install_macos_tools.sh

.buildkite/x-pack/pipeline.xpack.packetbeat.yml

@@ -264,7 +264,7 @@ steps:
 
   - group: "x-pack/packetbeat MacOS Extended Tests"
     key: "x-pack-packetbeat-extended-macos-tests"
-    if: build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
+    if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*macOS.*/
     steps:
       - label: ":mac: MacOS Unit Tests"
         key: "extended-macos-unit-tests"