[SDTEST-1786] Document new flaky tests metric of Flaky Test Management (

DataDog#30278)

* add flaky test metric docs

* pr feedback

* remove flaky_category from docs

[SDTEST-1673] Update audit trail events for Flaky Test Management (Da…

…taDog#28707)

add apm trace id to llmobs span intake endpoint (DataDog#30022)

* add apm trace id to llmobs span intake endpoint

* remove double

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Co-authored-by: kyle <kyle@verhoog.ca>

add clustername to install snippets (DataDog#30351)

Update issue_correlation.md (DataDog#30346)

Add spreadsheet to restriction_policy specs (DataDog#30335)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

chore: fix datadog-ci parameter typo (DataDog#30340)

Fix heading level (DataDog#30345)

[DOCS-11274] Restructure and simplify OP setup docs (DataDog#30280)

* restructure and update

* fix merge and duplication headers

* small edit

* update images and docs

* updates to setup and install docs

* revert use case docs changes

* Update content/en/observability_pipelines/use_cases.md

* update landing page

* revert changes

* remove unused image

* revert update

* fix links

* edit

* Apply suggestions from code review

Co-authored-by: cecilia saixue watt <cecilia.watt@datadoghq.com>

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Co-authored-by: cecilia saixue watt <cecilia.watt@datadoghq.com>

[DEBUG-4130] Remove preview banner for Code Origins (DataDog#30313)