RFR: 7903659 Verify Problemlist contents [v7]

[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:

  var

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Changes:
  - all: https://git.openjdk.org/jtreg/pull/181/files
  - new: https://git.openjdk.org/jtreg/pull/181/files/a47c1edd..966deea1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=06
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=181&range=05-06

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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