RFR: 8318106: Generated HTML for snippet does not always contain an id

[Pavel Rappo]

Please review this jdk24 bug, which we intend to backport to jdk23 before RDP2, which is a week away. This is a simple fix, but it disturbs multiple tests.

Here's a tip for reviewing. Sometimes a snippet id in a test ends up with `()1`, other times with `()2`. This is because the same snippet may appear more than once on the same page, and we are always looking for its last appearance. For example, if a snippet resides in the first sentence of a method documentation, that snippet will appear in both the "Method Summary" and "Method Details" sections. Otherwise, it will only appear in "Method Details". Appearances are numbered starting from 1 and increment by 1 from top ("Method Summary") to bottom ("Method Details").

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/20136/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20136&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318106
  Stats: 62 lines in 7 files changed: 43 ins; 0 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/20136.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20136/head:pull/20136

PR: https://git.openjdk.org/jdk/pull/20136