RFR: (XS): 8213570: [TESTBUG] Update JFR sanity test set

[Mikhailo Seledtsov]

Please review this*two-liner *update to JFR sanity test group.
After discussions with Erik, Markus and Leonid, we have agreed to add 
the following tests to jdk_jfr_sanity group:
   startupargs/TestDumpOnExit.java
   event/metadata/TestDefaultConfigurations.java

TestDefaultConfigurations.java is very useful, found a number of bugs in 
the past, and good in catching issues when developers/maintainers add 
new events
TestDumpOnExit.java tests commonly used mode of operation

Diff:
--- a/test/jdk/TEST.groups
+++ b/test/jdk/TEST.groups
@@ -460,7 +460,9 @@
      jdk/jfr/event/runtime/TestClassLoadEvent.java \
      jdk/jfr/event/runtime/TestJavaBlockedEvent.java \
      jdk/jfr/event/gc/collection/TestGCWithFasttime.java \
- jdk/jfr/event/gc/configuration/TestGCConfigurationEvent.java
+ jdk/jfr/event/gc/configuration/TestGCConfigurationEvent.java \
+ jdk/jfr/event/metadata/TestDefaultConfigurations.java \
+ jdk/jfr/startupargs/TestDumpOnExit.java


Testing: ran the group 20 times on multiple platforms, ALL PASS

Thank you,
Misha