Single file support WIP #11884

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	18m 44s
Gradle MacOS integration	1h 9m 9s
windows-latest jdk-17 unit tests 2 / 2	16m 0s
Sbt integration	34m 8s
macOS-latest jdk-17 unit tests 1 / 2	23m 0s
Maven integration	6m 54s
macOS-latest jdk-17 unit tests 2 / 2	16m 20s
Gradle integration	7m 14s
ubuntu-latest jdk-17 unit tests 1 / 2	17m 15s
Scala CLI integration	10m 41s
ubuntu-latest jdk-17 unit tests 2 / 2	11m 49s
ubuntu-latest jdk-8 unit tests 1 / 2	14m 30s
Mill integration	8m 29s
ubuntu-latest jdk-8 unit tests 2 / 2	14m 54s
LSP integration tests	25m 3s
Scala cross tests	41m 47s
Formatting	40s
Scalafix and docs	6m 24s
Sbt-metals/scripted jdk8	1m 45s
Scala javapc tests	2m 16s
Scala3 latest NIGHTLY cross test	3m 32s
Scala 2.11 cross tests	5m 45s
MiMa	1m 2s
	5h 57m 21s

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