enable scala 2 inliner (#246) #708

Job	Run time
sbt scripted tests (gen-scala-server, 2.12)	11m 34s
Compile and test (2.12.18, 8)	9m 32s
Compile Benchmarks	3m 43s
sbt scripted tests (gen-java, 2.12)	6m 43s
Compile and test (2.12.18, 11)	6m 37s
Checks	4m 43s
Compile and test (2.13.12, 8)	13m 10s
Compile and test (2.13.12, 11)	7m 6s
Gradle tests	6m 13s
Docs	5m 47s
Compile and test (3.3.1, 8)	7m 0s
Compile and test (3.3.1, 11)	7m 35s
Maven tests	5m 40s
	1h 35m 23s

Provide feedback