CI Default Intelligence - Tests v2, Cache Intel GA, DLC GA

[aimurphy]

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Description

• Please describe your changes: Cache Intelligence GA + Available to all Infras. Harness-managed DLC GA + Available to all Infras. Tests v2 beta (Test step) + preliminary deprecation of Tests v1 (Run Tests step).
• Jira/GitHub Issue numbers (if any): Multiple, including CI-11953
• Preview links/images (Internal contributors only):
  • Replace references & code samples for "Run Tests" step with "Test" step, with the exception of C# (Test v2 does not yet support C# TI).
  • Update Development Guides to show Cache Intelligence for all infras & use Test step where possible.
  • CI Feature Flag updates for GA & new Test step.
  • New Harness CI Intelligence page.
  • Revise CI overview page.
  • Update docker layer caching option descriptions on Build & Push step pages & some other pages.
  • Update Docker Layer Caching page to include all-infra support for Harness-managed DLC.
  • Update Cache intelligence page to include all-infra support.
  • Remove references to Cache Intelligence being only for Harness Cloud.
  • Include instructions to configure s3 global object store in Default Settings.
  • Run tests in CI: Use Test or Run step.
  • Split tests topic: Now called "Split Tests in Run steps" and exclusively focuses on splitting tests in Run steps.
  • Old "Run tests" topics are now in a "Run Tests step (deprecated)" category with a deprecation notice on each page.
  • Moved the TI overview topic up one level, renamed it, and revised it to focus on the Test step (It also includes the Run Test step minimally)
  • Deprecate "Java error tracking" on View builds page.
  • update feature compatibility matrix.
  • Update links & add redirects as needed for all above changes.
  • Update CI landing page generally.
  • Minimal modifications to FAQ/Troubleshooting per deprecation of Run Test step.
  • Draft (commented out) release notes for these features, to be updated when actually released.
  • Get rid of unhelpful "optimize" category (original/current prod link). Remove "Optimize" topic and disperse the information into more relevant locations (such as the DLC page and the Pipeline overview page). Move Step groups topic to /docs/platform/pipelines, since step groups aren't exclusive to CI. Move CI Environment variables reference to Troubleshoot CI (for now).

PR lifecycle

We aim to merge PRs within one week or less, but delays happen sometimes.

If your PR is open longer than two weeks without any human activity, please tag a code owner in a comment.

PRs must meet these requirements to be merged:

• [ ] Successful preview build.
• [ ] Code owner review.
• [ ] No merge conflicts.
• [ ] Release notes/new features docs: Feature/version released to at least one prod environment.