8340818: Add a new jtreg test root to test the generated documentation

[nizarbenalla]

Please review this change that adds a new test root docs dedicated to testing the documentation, which has been a work in progress for a while. Testings for links, encoding, HTML, accessibility will be later added in following PRs.

We also define a new make target test-docs meant for local use and depends on the docs.
This also adds the necessary configurations needed at Oracle.

TIA

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8340818: Add a new jtreg test root to test the generated documentation (Bug - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/21272/head:pull/21272
$ git checkout pull/21272

Update a local copy of the PR:
$ git checkout pull/21272
$ git pull https://git.openjdk.org/jdk.git pull/21272/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 21272

View PR using the GUI difftool:
$ git pr show -t 21272

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/21272.diff

[bridgekeeper]

👋 Welcome back nbenalla! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@nizarbenalla The following label will be automatically applied to this pull request:

• build

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.