RFR: 7903840: apidiff: optionally show expansion of `--jdk-build`

[Jonathan Gibbons]

Please review a small-ish PR to add support for `--verbose options` which outputs details about the upfront option handling.

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Commit messages:
 - fix test compilation failure, and fix some IDE suggestions
 - CODETOOLS-7903840: apidiff: optionally show expansion of `--jdk-build`

Changes: https://git.openjdk.org/apidiff/pull/19/files
  Webrev: https://webrevs.openjdk.org/?repo=apidiff&pr=19&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903840
  Stats: 120 lines in 6 files changed: 99 ins; 1 del; 20 mod
  Patch: https://git.openjdk.org/apidiff/pull/19.diff
  Fetch: git fetch https://git.openjdk.org/apidiff.git pull/19/head:pull/19

PR: https://git.openjdk.org/apidiff/pull/19