Support Jcmd dump with default settings

[JasonFengJ9]

Support Jcmd dump with default settings

DiagnosticUtils.triggerDumpsImpl() can generate dump files with default settings when the dump request doesn't have :file=name, modified the request string according to the incoming arguments.
Modified Jcmd help message;
Modified the test to adopt Jcmd without command argument;
Added a test for Jcmd with default settings;
Minor refactoring.

closes: #8721

Reviewer: @DanHeidinga
FYI: @pshipton

Signed-off-by: Jason Feng fengj@ca.ibm.com

[pshipton]

lgtm, it's worth extending the test suite though.
https://github.com/eclipse/openj9/blob/e741d649eeec1c687d0ac2fd29f8faffee38989f/test/functional/Java8andUp/src/org/openj9/test/attachAPI/TestJcmd.java#L178

[pshipton]

jenkins compile zlinux jdk11

[pshipton]

I tried the existing TestJcmd_0 test using a grinder, and it's failing.
https://ci.eclipse.org/openj9/view/Test/job/Grinder/644/

16:47:40  FAILED: testCommandNoOptions
16:47:40  java.lang.AssertionError: Expected string "Error: wrong number of arguments" not found expected [true] but found [false]
16:47:40  	at org.testng.Assert.fail(Assert.java:96)
16:47:40  	at org.testng.Assert.failNotEquals(Assert.java:776)
16:47:40  	at org.testng.Assert.assertTrue(Assert.java:44)
16:47:40  	at org.openj9.test.attachAPI.TestJcmd.testCommandNoOptions(TestJcmd.java:136)

[JasonFengJ9]

It is an extended test, that's why it didn't show up in the personal builds.
Will address the test failure and add the new test for the dump file with default settings.

[JasonFengJ9]

Modified/added the test, and passed locally.
Please review.

[pshipton]

jenkins test extended win,plinux jdk8,jdk11

[pshipton]

@JasonFengJ9 we should mention this change in the User Guide What's New. Pls create a docs Issue, and later a PR. The docs aren't open for 0.20.0 changes yet, but should be later this week.