RFR: 7903659 Verify Problemlist contents [v9]

[Ludvig Janiuk]

> This change introduces the flag `--verify-exclude` (short form `-i`) 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 one additional commit since the last revision:

  wording and indentation

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

Changes:
  - all: https://git.openjdk.org/jtreg/pull/181/files
  - new: https://git.openjdk.org/jtreg/pull/181/files/802f470c..9a9a5f21

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=08
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=07-08

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 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