build: sort Gradle config into more reusable pieces with less redundancy

[jjohannes]

Description:

As preparation to move things into a separate repository. (WiP)

Candidates for separate PRs:

• move:gradle/versions
• move gradle/aggregation and use for consistent resolution
• Publishing, developers.properties, description.txt
• gradle/jdk-version.txt

Related issue(s):

#14255

Notes for reviewer:

Checklist

• [ ] Documented (Code comments, README, etc.)
• [ ] Tested (unit, integration, etc.)