feat: custom project root setting #11596

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	33m 13s
Gradle MacOS integration	10m 22s
windows-latest jdk-17 unit tests 2 / 2	25m 31s
Sbt integration	48m 51s
macOS-latest jdk-17 unit tests 1 / 2	31m 19s
Maven integration	10m 18s
macOS-latest jdk-17 unit tests 2 / 2	23m 32s
Gradle integration	8m 37s
ubuntu-latest jdk-17 unit tests 1 / 2	17m 50s
Scala CLI integration	17m 49s
ubuntu-latest jdk-17 unit tests 2 / 2	18m 22s
Mill integration	16m 34s
ubuntu-latest jdk-8 unit tests 1 / 2	19m 0s
LSP integration tests	43m 8s
ubuntu-latest jdk-8 unit tests 2 / 2	20m 37s
Scala cross tests	59m 25s
Formatting	58s
Scalafix and docs	9m 53s
Sbt-metals/scripted jdk8	1m 37s
Scala javapc tests	2m 21s
Scala3 latest NIGHTLY cross test	5m 0s
MiMa	47s
	7h 5m 4s

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