RFR: 8365262: [IR-Framework] Add simple way to add cross-product of flags [v8]

[Manuel Hässig]

> This PR adds the `TestFramework::addCrossProductScenarios` method to enable more ergonomic testing of the combination of all flag combinations. To illustrate its use, I also converted one test to use the new cross product functionality.
> 
> Testing:
>  - [x] Github Actions
>  - [x] tier1,tier2 plus some internal testing on Oracle supported platforms

Manuel Hässig has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 15 additional commits since the last revision:

 - Merge branch 'master' into JDK-8365262
 - Remove excess newline
 - Fix indentation
 - Improve comments
 - Fix copy pasta mistakes
 - Improvements prompted by Emanuel
 - Fix test
 - Better counting in tests
 - post processing of flags and documentation
 - Make the test work
 - ... and 5 more: https://git.openjdk.org/jdk/compare/e9d43624...771924f0

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26762/files
  - new: https://git.openjdk.org/jdk/pull/26762/files/2e36929f..771924f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26762&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26762&range=06-07

  Stats: 17729 lines in 623 files changed: 9992 ins; 5396 del; 2341 mod
  Patch: https://git.openjdk.org/jdk/pull/26762.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26762/head:pull/26762

PR: https://git.openjdk.org/jdk/pull/26762