The overhead of build scans seems to have brought us right to the limit
of the Maven JVM's heap. As a result, builds are occasionally failing
as the heap's been exhausted.

This commit increases the JVM's max heap.

Closes gh-22649

* gh-22614:
  Upgrade to Gradle Enterperise Maven Extension 1.6.0

Closes gh-22614

See gh-22614

* gh-22555:
  Polish "Add generated-snippets as output to test goal"
  Add generated-snippets as output to test goal

Closes gh-22555

See gh-22555

The generated snippets were not declared as an output to the
`spring-boot-actuator-autoconfigure` test goal so when the test was
pulled from the cache, it did not contain the `generated-snippets`
directory. This directory is required as an input to the Asciidoctor
plugin.

See gh-22555

* gh-22550:
  Disable extra scans for full profile.

Closes gh-22550

The extra scans were not disabled for the full profile, only the
regular profile.

See gh-22550

* gh-22089:
  Polish "Add Gradle Enterprise Extension"
  Add Gradle Enterprise Extension

Closes gh-22089

See gh-22089

This adds build caching and build scans.

The changes required disabling scans when using the maven invoker
plugin in order to not cause duplicate build scans when invoking other
maven builds. There is also an empty `.mvn` folder in the
spring-boot-starters project to prevent duplicate build scans as well
since there is no way to pass properties to the maven-javadoc-plugin.

The checkstyle plugin was causing a cache miss with the
`propertyExpansion` because it contains an absolute path. The absolute
path is now ignored and instead the files are added as inputs to the
checkstyle plugin. This only enables the local build cache. The remote
cache is not yet enabled.

On my local machine:

./mvnw clean install build times go from about 30 minutes to about 10 minutes.
./mvnw clean install -Pfull build times go from about 60 minutes to about 13 minutes.

See gh-22089

See gh-22543

See gh-22543

Update `DistributeCommand` so that regex patterns can be used to mark
artifacts that are optional and need not fail the release.

Closes gh-22543

Closes gh-22537

Closes gh-22536

Closes gh-22505

Closes gh-22512

Closes gh-22511

Closes gh-22507

See gh-22505

Closes gh-22382

Closes gh-22370

Closes gh-22371

Closes gh-22430

Closes gh-22429

Closes gh-22428

Closes gh-22427

Closes gh-22426