make tests faster

[markusicu]

• In CI, two or more workflows build a cldr-unicodetools.tgz which takes over 2 minutes. Do we need all of these?
  • Elango thinks that we probably don't need the one in cli-build-instructions.yml
• Maven test in parallel, using multiple processes
  • surefire forkCount: parallel testing #1368
  • but made tests flaky, and hid failures...
  • mvn test serially again #1376
• TestTestUnicodeInvariants takes over 3 minutes.
  • Split it into multiple test classes for better granularity / more parallel testing.
    • tried that in split TestTestUnicodeInvariants into multiple classes #1369, some tests failing
    • dependency on an earlier test run? race condition? debug?
    • maybe try to just split out the security invariants?
  • Idea: Try to turn many of the test cases into a parameterized test. Read each per-proposal file as a separate test case. Maybe even turn the large file into multiple test cases?
• TestPropertyAccess takes 2.5 minutes.
• jsptest.TestProperties takes half a minute.
• In CI, the longest-running task is Build JSPs/ Regenerate the property cache files
  • Takes some 12 minutes!
  • Maybe try to profile the code and look for good optimization ROI. Might end up making all of the tools/tests faster.

Notes

TestTestUnicodeInvariants.testAdditionComparisons() has this comment:

        // Ideally, this would be a @ParameterizedTest, and we would use the Dtest parameter of the
        // mvn command line to filter a specific test.
        // Unfortunately, this does not appear to be possible with JUnit 5 and Surefire, see
        // https://stackoverflow.com/questions/69198795/junit5-running-a-single-instance-of-parameterized-test,
        // so we have one big test and we filter by hand.
        final String rmgIssueFilter = CldrUtility.getProperty("RMG_ISSUE", null);