RFR: 8343832: Enhance test summary with number of skipped tests [v7]

[Ivan Bereziuk]

> The output for Jtreg v7.5 was [enhanced](https://github.com/openjdk/jtreg/pull/217/files#diff-b6ab77bf651f1fd9a83c3ca0aab9cd24ae5c08cef41e6e257f7eaccc07c7c366R947) with [information about skipped tests](https://github.com/openjdk/jtreg/blob/master/src/share/doc/javatest/regtest/faq.md#what-do-all-those-numbers-in-the-test-results-line-mean).
> 
> Use the additional information in the "summary" block printed at the end of `make test` target.

Ivan Bereziuk 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 11 additional commits since the last revision:

 - Merge branch 'master' into 8343832_enhance_test_summary
 - Merge branch 'master' into 8343832_enhance_test_summary
 - SKIPPED is always zero for Microbenchark testing. Define SKIPPED in one go after branching.
 - _SKIPPED was not defined for gtest and special tests. Treat disabled gtests as _SKIPPED
 - adapt changes to the ancient awk on MacOS
 - Merge branch 'master' into 8343832_enhance_test_summary
 - indented the comment
 - remove resorting zero-ing of $1_SKIPPED as preceding gawk always assigns the value
 - lowercased Jtreg. fixed typos in the comment
 - aggregated calculation for many categoires of skipped tests into one gawk block with regex
 - ... and 1 more: https://git.openjdk.org/jdk/compare/ba2b0c2b...6af586a2

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22245/files
  - new: https://git.openjdk.org/jdk/pull/22245/files/4a1a9268..6af586a2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22245&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22245&range=05-06

  Stats: 212999 lines in 5143 files changed: 102946 ins; 87626 del; 22427 mod
  Patch: https://git.openjdk.org/jdk/pull/22245.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22245/head:pull/22245

PR: https://git.openjdk.org/jdk/pull/22245