RFR: 7903373: Add ability to customize test execution using main wrapper plugin

[Leonid Mesnik]

The fix adds support of a plugin that customizes test execution.

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

Commit messages:
 - argumetns added
 - test fixed
 - fixed space
 - more identation fixes
 - identation fixed.
 - Merge branch 'master' of https://github.com/openjdk/jtreg into loom
 - fixes
 - Wrapper moved to JDK
 - ident
 - fix
 - ... and 29 more: https://git.openjdk.org/jtreg/compare/1ad8188f...7b9b8e93

Changes: https://git.openjdk.org/jtreg/pull/136/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=136&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903373
  Stats: 384 lines in 12 files changed: 374 ins; 1 del; 9 mod
  Patch: https://git.openjdk.org/jtreg/pull/136.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/136/head:pull/136

PR: https://git.openjdk.org/jtreg/pull/136