Search for Liberty modules to use in Run/Debug config

[turkeylurkey]

The fix for the bug is in LibertyRunConfiguration but to get that new method the logic needed to be extracted from the class LibertyExplorer. See the comment in the issue.

In the process of refactoring that method (buildTree()) I noticed that two loops did almost the same things for Gradle and Maven files so I combined them into one loop. A lot of code was removed. Also the module code that moved from LibertyExplorer to LibertyModules was two loops and they were combined into one. I added data validation to the class BuildFile mainly to document the acceptable values but also to ensure correctness.

I noticed that some error statements in the test log did not indicate that the test was going to retry and this confused me so I took the opportunity to change the output string by adding the word "Retrying..." like the other tests.

Fixes #1202

[turkeylurkey]

I tried to simplify the nested lambdas in LibertyProjectUtil.readIndex().

[turkeylurkey]

Investigating test failures.

[turkeylurkey]

Latest #5

Mac: MyList

MavenSingleModMPProjectTest > testMultipleConfigEditHistory() FAILED
com.intellij.remoterobot.utils.WaitForConditionTimeoutException: Exceeded timeout (PT10S) for condition function (Failed to find 'Container' by '//div[@Class='HeavyWeightWindow']//div[@Class='MyList']' in 10s)

at io.openliberty.tools.intellij.it.fixtures.ProjectFrameFixture.getMyList(ProjectFrameFixture.java:338)
152 tests completed, 1 failed, 16 skipped

Windows: messages.log

GradleSingleModMPProjectTest > testCustomStartParametersClearedOnConfigRemoval() FAILED
org.opentest4j.AssertionFailedError: testCustomStartParametersClearedOnConfigRemoval:validateLibertyServerStopped: Exit. Timed out waiting for message CWWKE0036I in log:D:\a\liberty-tools-intellij\liberty-tools-intellij\liberty-tools-intellij\src\test\resources\projects\gradle\singleModGradleMP\build\wlp\usr\servers\defaultServer\logs\messages.log

at io.openliberty.tools.intellij.it.TestUtils.validateLibertyServerStopped(TestUtils.java:106)
152 tests completed, 1 failed, 16 skipped

[turkeylurkey]

Since commit 35c3458 was added Linux passed and Windows failed with the same error as in the comment above ("Timed out waiting for message CWWKE0036I"). Mac: "Timed out waiting for message CWWKE0036I" and testMultipleConfigEditHistory().

[vaisakhkannan]

LGTM

[mrglavas]

Thanks for the demo. Looks good. I had a few minor comments, but shouldn't stop you from merging now.