Use isFirstSetupComplete instead isSyncRequested for isChromeSyncEnabled (uplift to 1.12.x)

[AlexeyBarabash]

Uplift of #6480

Resolves brave/brave-browser#11210, brave/brave-browser#11077, brave/brave-browser#11363

Created manually and had to re-do the PR merged to master

Approved, please ensure that before merging:

• You have checked CI and the builds, lint, and tests all pass or are not related to your PR.
• You have tested your change on Nightly.
• The PR milestones match the branch they are landing to.

After you merge:

• The associated issue milestone is set to the smallest version that the changes is landed on.

[kjozwiak]

test-unit failed on Android as per https://ci.brave.com/job/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-android/1/execution/node/193/log/. However, @mihaiplesa mentioned this is a known issue due to running the Android builds using the wrong labels. Will be resolved sometime today/tomorrow once @linhkikuchi comes online.

test-browser failed on Win x64 due to SpeedReaderBrowserTest.SmokeTest failing as per https://ci.brave.com/job/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-windows/1/execution/node/216/log/. However, this is a known intermittent failure and doesn't block uplift.

16:33:30  [  FAILED  ] SpeedReaderBrowserTest.SmokeTest, where TypeParam =  and GetParam() =  (2326 ms)
16:33:30  
16:33:30  [611/611] SpeedReaderBrowserTest.SmokeTest (2497 ms)
16:33:30  1 test failed:
16:33:30      SpeedReaderBrowserTest.SmokeTest (../../brave/browser/speedreader/speedreader_browsertest.cc:65)

Restarting macOS via https://ci.brave.com/job/brave-core-build-pr-macos/job/PR-6495/2/ as both test-unit and test-browser timed out as per https://ci.brave.com/job/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-macos/1/execution/node/206/log/ & https://ci.brave.com/job/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-macos/1/execution/node/219/log/.

[AlexeyBarabash]

Android CI failed on test-unit

23:27:27  -------------------------------
23:27:27  /home/ubuntu/workspace/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-android/src
23:27:27  > /home/ubuntu/workspace/pr-brave-browser-pr6480_android_sync_fix_11363_1.12.x-android/src/out/android_Release_x86/brave_unit_tests --enable-logging=stderr --test-launcher-jobs=4
23:27:27  W    0.596s Main  No devices found. Will try again after restarting adb server and a short nap of 2 s.
23:27:29  W    3.927s Main  No devices found. Will try again after restarting adb server and a short nap of 4 s.
23:27:36  W    9.259s Main  No devices found. Will try again after restarting adb server and a short nap of 8 s.
23:27:44  W   18.565s Main  No devices found. Will try again after restarting adb server and a short nap of 16 s.
23:28:02  W   35.909s Main  Attempting to reset relevant USB devices prior to the last attempt.
23:28:02  W   36.216s Main  No devices found. Will try again after restarting adb server and a short nap of 32 s.
23:28:41  E   69.577s Main  No devices found after exhausting all retries.
23:28:41  E   69.579s Main  Error occurred.

Windows CI failed though only Android java files touched

23:33:30  1 test failed:
23:33:30      SpeedReaderBrowserTest.SmokeTest (../../brave/browser/speedreader/speedreader_browsertest.cc:65)

[AlexeyBarabash]

Closed after discussion with @kjozwiak