RFR: 7903786: Allow JCov to read zip files

[Alexandre Iline]

This is the first step of implementing [CODETOOLS-7903650](https://bugs.openjdk.org/browse/CODETOOLS-7903650)

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Commit messages:
 - CODETOOLS-7903786: Allow JCov to read zip files

Changes: https://git.openjdk.org/jcov/pull/45/files
  Webrev: https://webrevs.openjdk.org/?repo=jcov&pr=45&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903786
  Stats: 150 lines in 2 files changed: 130 ins; 14 del; 6 mod
  Patch: https://git.openjdk.org/jcov/pull/45.diff
  Fetch: git fetch https://git.openjdk.org/jcov.git pull/45/head:pull/45

PR: https://git.openjdk.org/jcov/pull/45