8345136: Update JDK_DOCS property to point to JDK 23 docs

[kevinrushforth]

Update the docs bundle to point to the JDK 23 docs (we're currently pointing to JDK 21).

I will need to also download and host a zip bundle and add its checksum to gradle/verification-metadata.xml to avoid breaking our internal CI build.

As mentioned in JDK-8325873 when we updated the docs to use JDK 21, we should do this as a part of updating the boot JDK. To facilitate this, and to move more version number properties to a common place, I will create a new jdk.docs.version property in build.properties and put it near the jfx.build.jdk.version property.

Both the GHA build and our CI build are successful.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8345136: Update JDK_DOCS property to point to JDK 23 docs (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jfx.git pull/1663/head:pull/1663
$ git checkout pull/1663

Update a local copy of the PR:
$ git checkout pull/1663
$ git pull https://git.openjdk.org/jfx.git pull/1663/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1663

View PR using the GUI difftool:
$ git pr show -t 1663

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jfx/pull/1663.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back kcr! 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.

[kevinrushforth]

Reviewers: @arapte or @andy-goryachev-oracle AND @tiainen or @johanvos

/reviewers 2

[openjdk]

@kevinrushforth
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[mlbridge]

Webrevs

• 00: Full (795ed9aa)