Cloud output v2 changelog (#3161)

Changelog entry for the Cloud output v2

---------

Co-authored-by: Oleg Bespalov <[email protected]>

release notes/v0.46.0.md

@@ -82,9 +82,19 @@ if (__ITER === 0) {
 
 Thanks @chrismoran-mica for contribution 🙇‍♂️.
 
-### `<big_feature_1>` `#pr`
+### Cloud Output v2 [#3117](https://github.com/grafana/k6/issues/3117)
 
-_what, why, and what this means for the user_
+After years of great service, we decided to refresh the k6 Cloud output introducing a more efficient end-to-end solution for ingesting the generated tests' metrics. The main change regards the protocol used for flushing metrics that is now a binary based payload over HTTP.
+
+The new output reduces the load generators' used resources for tests that produce many metrics. There is no significant difference in the user experience; it's expected to be the same. 
+
+The one thing worth highlighting is that the new output is strict about tags and drops tags if they are reserved:
+- `test_run_id` as it is reserved for internal k6 Cloud operations
+- any tag with a key that starts with two underscores (`__`), that is marked by Prometheus convention as reserved
+
+At the moment this is not yet the default Cloud output for the test runs executed from local machines (`k6 run -o cloud`), but it is expected to be transparently enabled in the upcoming weeks.
+
+The full list of related PRs: [#3104](https://github.com/grafana/k6/pull/3104), [#3108](https://github.com/grafana/k6/pull/3108), [#3120](https://github.com/grafana/k6/pull/3120), [#3125](https://github.com/grafana/k6/pull/3125), [#3162](https://github.com/grafana/k6/pull/3162), [#3169](https://github.com/grafana/k6/pull/3169), [#3182](https://github.com/grafana/k6/pull/3182), [#3186](https://github.com/grafana/k6/pull/3186), [#3187](https://github.com/grafana/k6/pull/3187), [#3193](https://github.com/grafana/k6/pull/3193), [#3195](https://github.com/grafana/k6/pull/3195), [#3206](https://github.com/grafana/k6/pull/3206), [#3226](https://github.com/grafana/k6/pull/3226), [#3157](https://github.com/grafana/k6/pull/3157), [#3172](https://github.com/grafana/k6/pull/3172).
 
 ### `<big_feature_n>` `#pr`
 
@@ -95,7 +105,6 @@ _what, why, and what this means for the user_
 _Format as `<number> <present_verb> <object>. <credit>`_:
 - _`#999` Gives terminal output prettier printing. Thanks to `@person` for the help!_
 
-- [#3157](https://github.com/grafana/k6/pull/3157) and [#3172](https://github.com/grafana/k6/pull/3172) Add a `MaxTimeSeriesInBatch` configuration option.
 - [#3176](https://github.com/grafana/k6/pull/3176) Adds a `js/promises` package, which enables extension developers to easily create promises that will be dispatched to the eventloop using the `New` function.
 - [#3181](https://github.com/grafana/k6/pull/3181) Adds a `RunOnEventLoop` method to the `modulestest.Runtime` type, which allows extensions developers to run code on the event loop from their tests.
 
@@ -116,24 +125,6 @@ _Format as `<number> <present_verb> <object>. <credit>`_:
 - [#3131](https://github.com/grafana/k6/pull/3131) Updates our Pull Request template to be more structured and include a checklist for contributors.
 - [#3177](https://github.com/grafana/k6/pull/3177) Updates the version of golangci-lint we use to the latest version.
 
-### Cloud output v2
-
-// TODO @codebien
-
-* [3104](https://github.com/grafana/k6/pull/3104) Retry and flushers pool
-* [3108](https://github.com/grafana/k6/pull/3108) Flush chunks
-* [3120](https://github.com/grafana/k6/pull/3120) Unlimited size for body payload
-* [3125](https://github.com/grafana/k6/pull/3125) Use a static remote service url
-* [3162](https://github.com/grafana/k6/pull/3162) Warn about labels that have reserved names
-* [3169](https://github.com/grafana/k6/pull/3169) Compact histogram
-- [#3182](https://github.com/grafana/k6/pull/3182) Fix off-by-one error for spans
-- [#3186](https://github.com/grafana/k6/pull/3186) Be less noisy when handling errors
-- [#3187](https://github.com/grafana/k6/pull/3187) Create batches for single bucket flush
-- [#3193](https://github.com/grafana/k6/pull/3193) Downscale the batch size
-- [#3195](https://github.com/grafana/k6/pull/3195) Make sure to use the overwritten config
-- [#3206](https://github.com/grafana/k6/pull/3206) Implement concurrent pushes accross batches
-- [#3226](https://github.com/grafana/k6/pull/3226) don't go over maxSeriesInBatch
-
 ## _Optional_ Roadmap
 
 _Discussion of future plans_