RFR: 7903097: jtreg could implement ToolProvider [v7]

[Christian Stein]

> Implement `ToolProvider`, now that the main `jtreg` tool requires JDK >= 9.

Christian Stein has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 11 commits:

 - Merge branch 'master' into 7903097-implement-toolprovider
 - Fix indentation
   
   [skip actions]
 - Fix java source launcher call
 - Apply suggested changes
 - Prevent non-zero exit code by using supported option
 - Move `ToolProvider`-related test into a dedicated folder
 - Update more expected numbers
 - Expect another passing test
 - Re-use I18N messages by moving `JtregToolProvider` to `tool` package
 - Add rule to copy service-related resource files
 - ... and 1 more: https://git.openjdk.java.net/jtreg/compare/cdcd462f...49c11b09

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

Changes: https://git.openjdk.java.net/jtreg/pull/54/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jtreg&pr=54&range=06
  Stats: 156 lines in 6 files changed: 155 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/54.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/54/head:pull/54

PR: https://git.openjdk.java.net/jtreg/pull/54