RFR: JMH Pre-Integration Tests workflow [v2]

[Aleksey Shipilev]

> This adds the basic pre-integration test workflow for the project.

Aleksey Shipilev 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 ten additional commits since
the last revision:

 - Merge branch 'master' into gh-actions
 - Disable commit on push
 - Merge branch 'master' into gh-actions
 - Merge branch 'master' into gh-actions
 - Merge branch 'master' into gh-actions
 - Drop max-parallel from pre-integration workflow
 - Testing more extensive configuration space
 - Mention pre-integration workflow in README
 - Basic pre-integration workflow for JMH

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Changes:
  - all: https://git.openjdk.java.net/jmh/pull/5/files
  - new: https://git.openjdk.java.net/jmh/pull/5/files/2ca6af4f..fa39616f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmh&pr=5&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jmh&pr=5&range=00-01

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jmh/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/5/head:pull/5

PR: https://git.openjdk.java.net/jmh/pull/5