Improves spotlessPredeclare

[bric3]

This PR introduces two changes

• Make spotlessPredeclare visible to Gradle Kotlin DSL type-safe accessors.
• Allow spotlessPredeclare to be used directly without enabling it first in spotless extension.

Now the spotlessPredeclare can be used on the root project directly

spotlessPredeclare { java { ... } }

spotlessPredeclare { fromBuildscriptRepositories() java { ... } }

before one had to write respectively

import com.diffplug.gradle.spotless.SpotlessExtension spotless { predeclareDeps() } with(extensions["spotlessPredeclare"] as SpotlessExtension) { java { ... } }

import com.diffplug.gradle.spotless.SpotlessExtension spotless { predeclareDepsFromBuildscript() } with(extensions["spotlessPredeclare"] as SpotlessExtension) { java { ... } }

Note I intentionally, kept the old API to be backward compatible.

Also fixes #2580

[bric3]

Two jobs failure appear to be infrastructure issues

[jochenberger]

Two jobs failure appear to be infrastructure issues

#2928 should fix that.

[bric3]

Thanks @jochenberger