RFR: 7903160: Run self-tests for jtreg on MacOS and Windows [v14]

[Christian Stein]

> CI builds including self-tests for `jtreg` are run on Linux.
> 
> Now, they also run on MacOS and Windows.

Christian Stein has updated the pull request incrementally with two additional commits since the last revision:

 - Rename .github/actions/build.yml to .github/actions/build/action.yml
 - One job per OS

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Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/75/files
  - new: https://git.openjdk.java.net/jtreg/pull/75/files/06c707e9..56cd9a09

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=13
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=12-13

  Stats: 49 lines in 2 files changed: 0 ins; 31 del; 18 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/75.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/75/head:pull/75

PR: https://git.openjdk.java.net/jtreg/pull/75