RFR: 7903867: Add a test for RepGen

[Alexandre Iline]

Please note that a test for repine could also be written with just processing of a coverage xml file.
Please also notice that the command line test execution is blocked by https://bugs.openjdk.org/browse/CODETOOLS-7903035

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Commit messages:
 - CODETOOLS-7903867: Add a test for RepGen

Changes: https://git.openjdk.org/jcov/pull/50/files
  Webrev: https://webrevs.openjdk.org/?repo=jcov&pr=50&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903867
  Stats: 148 lines in 2 files changed: 148 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jcov/pull/50.diff
  Fetch: git fetch https://git.openjdk.org/jcov.git pull/50/head:pull/50

PR: https://git.openjdk.org/jcov/pull/50