feat: add test cases discovery for TestNG #14750

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	30m 35s
Gradle MacOS integration	11m 14s
windows-latest jdk-17 unit tests 2 / 2	30m 28s
Sbt integration	48m 38s
macOS-latest jdk-17 unit tests 1 / 2	54m 30s
Maven integration	8m 32s
macOS-latest jdk-17 unit tests 2 / 2	51m 48s
Gradle integration	9m 29s
ubuntu-latest jdk-17 unit tests 1 / 2	18m 28s
ubuntu-latest jdk-17 unit tests 2 / 2	18m 40s
Scala CLI integration	14m 52s
Mill integration	35m 30s
Bazel integration	10m 26s
LSP integration tests	33m 17s
Scala cross tests	33m 38s
Formatting	32s
Scalafix and docs	4m 55s
Sbt-metals/scripted jdk11	2m 50s
sbt-metals/scripted (Sbt 2)	1m 37s
Scala javapc tests	1m 51s
Scala 2.11 cross tests	4m 4s
MiMa	1m 2s
	7h 6m 56s

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