RFR: 7902876: Cleanup Instr tool

[Leonid Kuskov]

This is the fix for https://bugs.openjdk.java.net/browse/CODETOOLS-7902876
The update fixes the following
1. usage of methods in utests should be downgraded to JDK 8
2. spelling errors and malformed comments
3. javap regression
4. jcov should be switched from 9.0.1 snapshot to 9.1 (JDK 17 is supported)
5. deprecated methods should be refactored

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Commit messages:
 - 7902876: Cleanup Instr tool
 - Instrumentation plugin concept
 - 7902764: RepGen: Javap mode doesn't support classes that have no package
 - 7902724: jcov ignores covariant method overriding while gathering a methods coverages
 - Merge remote-tracking branch 'upstream/master'
 - 7902819: jcov fails to instrument JDKs records
 - Merge branch 'master' into CODETOOLS-7902823
 - 7902823: RepGen fails with IllegalFormatArgumentIndexException if started by JDK 16 and above
 - Merge remote-tracking branch 'upstream/master'
 - 7902796: Provide a "release" file for JCov builds
 - ... and 8 more: https://git.openjdk.java.net/jcov/compare/19a1a119...aba9f91b

Changes: https://git.openjdk.java.net/jcov/pull/12/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcov&pr=12&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902876
  Stats: 1283 lines in 26 files changed: 926 ins; 94 del; 263 mod
  Patch: https://git.openjdk.java.net/jcov/pull/12.diff
  Fetch: git fetch https://git.openjdk.java.net/jcov pull/12/head:pull/12

PR: https://git.openjdk.java.net/jcov/pull/12