RFR: 8333146: Move maven publication logic from build.gradle [v5]

[Marius Hanl]

> This PR splits the maven publishing logic into an own file, `maven-publish.gradle`, that is next to the root `build.gradle`.
> 
> The `build.gradle` will apply the `maven-publish.gradle`. The `maven-publish.gradle` will then configure the Maven related properties and register all modules for publication.
> 
> This way, we decoupled the logic that much, the only things we need to do:
> - apply from `maven-publish.gradle`
> - Call `configureMavenPublication` later in the build chain.
> 
> To better understand the context, this is the commit where the whole Maven Publishing logic was introduced. I moved all of that logic out of the main `build.gradle`: 5a18677f
> 
> This will reduce the size by ~170 lines for the `build.gradle`.
> 
> Tested with:
> - `./gradlew -PMAVEN_PUBLISH=true -PMAVEN_VERSION=custom publishToMavenLocal`
> - `./gradlew -PMAVEN_PUBLISH=true publishToMavenLocal`
> - `./gradlew -PMAVEN_PUBLISH=true -PMILESTONE_FCS=true publishToMavenLocal`
> 
> Everything still works:
> -> Example: javafx.base from the local .m2 repository
> <img width="1051" height="388" alt="image" src="https://github.com/user-attachments/assets/66ccd007-ff2c-4309-982a-1e8123e9f52a" />
> 
> I think this is a good step and an easy way to split out functionality without blowing things up. We might want to do that for other parts as well.
> 
> Note: I also fixed the deprecated `buildDir`, the deprecated `project.task` method and 2 warnings where it seems like he might not be able to infer the type (changing `def` to the actual type). 
> -> The file is completely green, no warnings or deprecations.
> Note2: I did a small improvement to the `addMavenPublication` method. It is now more 'typesafe', e.g. projects must be passed in directly, not as String. If a project does not exist, the build will fail with an exception.

Marius Hanl has updated the pull request incrementally with one additional commit since the last revision:

  Depend maven publishing on the build modules task

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1970/files
  - new: https://git.openjdk.org/jfx/pull/1970/files/ea0b427c..6d8e7282

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1970&range=04
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1970&range=03-04

  Stats: 18 lines in 2 files changed: 7 ins; 8 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1970.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1970/head:pull/1970

PR: https://git.openjdk.org/jfx/pull/1970