RFR: 7903659 Verify Problemlist contents [v2]

[Ludvig Janiuk]

> This change introduces the flag `-verifyexclude` which will run additional checks on the problemlists passes through `-exclude`. If any of the checks fails, jtreg prints a helpful message and refuses to start running tests.

Ludvig Janiuk has updated the pull request incrementally with five additional commits since the last revision:

 - copyright, more
 - copyright
 - Pattern.compile
 - formatting, pass explicit PrintWriter
 - Return empty array, not null

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

Changes:
  - all: https://git.openjdk.org/jtreg/pull/181/files
  - new: https://git.openjdk.org/jtreg/pull/181/files/60f1f777..692fd019

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=01
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=00-01

  Stats: 69 lines in 7 files changed: 38 ins; 4 del; 27 mod
  Patch: https://git.openjdk.org/jtreg/pull/181.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/181/head:pull/181

PR: https://git.openjdk.org/jtreg/pull/181