RFR: 7904080: APIDiff does not detect javadoc (and changes to javadoc) for methods with varargs

[Jan Lahoda]

The keys in the HTML Javadoc for methods with varargs use `...`, but the signatures generated by API Diff use `[]`, so API Diff cannot find the appropriate javadoc in the HTML for vararg methods, which leads to a failure to show the differences in the javadoc for such methods.

There are multiple possible ways to fix that, but the proposal herein is to try to normalize the keys to use `[]` while reading the HTML.

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Commit messages:
 - 7904080: APIDiff does not detect javadoc (and changes to javadoc) for methods with varargs

Changes: https://git.openjdk.org/apidiff/pull/31/files
  Webrev: https://webrevs.openjdk.org/?repo=apidiff&pr=31&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904080
  Stats: 10 lines in 2 files changed: 8 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/apidiff/pull/31.diff
  Fetch: git fetch https://git.openjdk.org/apidiff.git pull/31/head:pull/31

PR: https://git.openjdk.org/apidiff/pull/31