RFR: CODETOOLS-7903317: Fix code to compile extra property definitions [v2]

[Jonathan Gibbons]

> Please review a fairly simple update to eliminate false positives in comments when looking for the name of the class in a Java source file.
> 
> The fix addresses a performance issue when running tests, because the "extra property definition" files were compiled every time jtreg was run, instead of as needed, which is the intent.
> 
> The fix is to ignore comments in the source code. The code to do this is copied from equivalent functionality in the langtools `ToolBox` class, which has been in use for many years.
> 
> The existing tests for "extra property definition" files have been extended with a test case to ensure that the false positives no longer occur and that the files are not recompiled unnecessarily.
> 
> Minor style issues in the main source file have also been fixed.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

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

Changes:
  - all: https://git.openjdk.org/jtreg/pull/122/files
  - new: https://git.openjdk.org/jtreg/pull/122/files/e06107c0..3dd8daae

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=122&range=01
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=122&range=00-01

  Stats: 29 lines in 21 files changed: 0 ins; 28 del; 1 mod
  Patch: https://git.openjdk.org/jtreg/pull/122.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/122/head:pull/122

PR: https://git.openjdk.org/jtreg/pull/122