Add missing copyright header

Add missing TestUtils class for testing onError

Fix typos

Add tests for onError

8231471: Obsolete -XX:CompilationPolicyChoice Reviewed-by: kvn, dholmes, thartmann

8231405: [Shenandoah] guarantee(d != NULL) failed: Null dominator info Reviewed-by: shade, rkennke

8231504: Update networking tests to avoid implicit dependency on the system proxies Reviewed-by: dfuchs

8228625: [TESTBUG] sun/tools/jhsdb/JShellHeapDumpTest.java fails with RuntimeException 'JShellToolProvider' missing from stdout/stderr Summary: Give jshell process time to fully startup and stablize before requesting heap dump Reviewed-by: sspitsyn, amenkov

8231546: Suppress warnings on non-serializable instance fields in java.prefs module Reviewed-by: rriggs

8231314: java.time serialization warning cleanup Reviewed-by: chegar, naoto, plevart

8231467: Missing make prerequisite declaration corrupts make dependency files on Windows Reviewed-by: ihse, tbell

8231382: Use main class from main module if available Submitted-by: almatvee Reviewed-by: herrick, asemenyuk

8230649 : Make jpackage tool an experimental feature Reviewed-by: asemenyuk, kcr

8226690: SIGSEGV in MetadataOnStackClosure::do_metadata Summary: Dont create nmethod if classes have been redefined since compilation start. Reviewed-by: sspitsyn, dlong, eosterlund, gdub

Incorporate CSR feedback

8231448: s390 and ppc - replace JVM type comparisons to T_OBJECT and T_ARRAY with call to is_reference_type Reviewed-by: coleenp, lfoltan