improvement: add jdk indexing #13325

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	20m 58s
windows-latest jdk-17 unit tests 2 / 2	30m 3s
Gradle MacOS integration	10m 5s
macOS-12 jdk-17 unit tests 1 / 2	24m 30s
Sbt integration	46m 45s
Maven integration	8m 38s
macOS-12 jdk-17 unit tests 2 / 2	26m 42s
ubuntu-latest jdk-17 unit tests 1 / 2	18m 30s
ubuntu-latest jdk-17 unit tests 2 / 2	15m 38s
ubuntu-latest jdk-11 unit tests 1 / 2	17m 0s
Gradle integration	8m 51s
ubuntu-latest jdk-11 unit tests 2 / 2	17m 23s
Scala CLI integration	14m 5s
Mill integration	12m 52s
Bazel integration	10m 29s
LSP integration tests	30m 18s
Scala cross tests	43m 38s
Formatting	32s
Scalafix and docs	4m 53s
Sbt-metals/scripted jdk11	1m 37s
Scala javapc tests	1m 42s
Scala 2.11 cross tests	3m 55s
MiMa	37s
	6h 9m 41s

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