RFR: 8339570: Add Tidy build support for JDK tests [v14]

[Nizar Benalla]

> Can I get a review for this patch that adds the necessary changes for local support of the `tidy` library.
> 
> The dependency can be retrieved by running `make/devkit/createTidyBundle.sh` on Linux and MacOs systems.
> 
> This dependency is primarily going to be used to test the generated documentation.
> 
> This patch is meant to be integrated before #21272.
> 
> Note: we need to be a very specific revision of `tidy` and cannot use any of the available artifacts, as older versions do not recognize some HTML 5 elements. 
> 
> TIA

Nizar Benalla has updated the pull request incrementally with one additional commit since the last revision:

  lower case other usage of tidy_version

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21341/files
  - new: https://git.openjdk.org/jdk/pull/21341/files/a71aab92..3dbffd6e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21341&range=13
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21341&range=12-13

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21341.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21341/head:pull/21341

PR: https://git.openjdk.org/jdk/pull/21341