[jdk19] RFR: 8281969: Bad result for javadoc snippet (//@link) tag for White space substring/regex. [v3]

[Pavel Rappo]

> This PR fixes how links inside a snippet treat whitespace.
> 
> During the development of the "Snippets" feature, the concern was about presentation of links that contain leading or trailing whitespace. For that reason, any such whitespace was trimmed. I think it's now reasonable to simplify code and say that any such presentation concerns should be solved with presentation tools, such as CSS.

Pavel Rappo has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge remote-tracking branch 'jdk19/master' into 8281969
 - refactor: improve test infrastructure
   
   Clarifies comment. In particular, the fact that the linking mechanism is
   shared between the @link standard doclet tag and the similarly named
   snippet markup tag is not specified. It's the Programmer's Guide that
   mentions such sharing:
   
     https://docs.oracle.com/en/java/javase/18/code-snippet/index.html
   
   But that guide is not a specification.
 - fix: do not filter out whitespace in links

-------------

Changes:
  - all: https://git.openjdk.org/jdk19/pull/142/files
  - new: https://git.openjdk.org/jdk19/pull/142/files/f7b0cd0f..6b527778

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk19&pr=142&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk19&pr=142&range=01-02

  Stats: 7 lines in 5 files changed: 3 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk19/pull/142.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/142/head:pull/142

PR: https://git.openjdk.org/jdk19/pull/142