Add client progress for delegate commands

[hopehadfield]

Fixes #1186

[rgrunber]

This works, but there's a problem.

This behaviour seems similar to what's described in redhat-developer/vscode-java#3249 so maybe there's an existing bug in the progress report where some tasks don't received an end notification.

[rgrunber]

CC : @testforstephen

So I looked at one of the progress messages that hang :

[Trace - 16:36:54] Received notification '$/progress'.
Params: {
    "token": "b0a92711-cde3-4701-a8c3-a7b7a07a0f2f",
    "value": {
        "kind": "report",
        "message": "Background task - 75% Locating Java matches...",
        "percentage": 75
    }
}

and looked earlier at what kind of messages fall under b0a92711-cde3-4701-a8c3-a7b7a07a0f2f.

[Info  - 16:36:50] Aug. 30, 2023, 4:36:50 p.m. >> workspace/executeCommand vscode.java.test.findTestPackagesAndTypes
[Trace - 16:36:50] Received request 'window/workDoneProgress/create - (47)'.
Params: {
    "token": "b0a92711-cde3-4701-a8c3-a7b7a07a0f2f"
}

...
...

[Trace - 16:36:50] Received notification '$/progress'.
Params: {
    "token": "b0a92711-cde3-4701-a8c3-a7b7a07a0f2f",
    "value": {
        "kind": "begin",
        "title": "Searching for JUnit 5 tests...",
        "message": "Searching for JUnit 5 tests..."
    }
}

[Trace - 16:36:50] Received notification '$/progress'.
Params: {
    "token": "b0a92711-cde3-4701-a8c3-a7b7a07a0f2f",
    "value": {
        "kind": "report",
        "message": "Searching for JUnit 5 tests... - 0% ",
        "percentage": 0
    }
}

Looks to me like this is called by https://github.com/microsoft/vscode-java-test/blob/main/src/controller/testController.ts#L44-L67 whenever java.test.explorer.loadChildren occurs ? Probably when we load type hierarchy children ?

There's even an error from the delegate call on the JDT-LS side :

!ENTRY com.microsoft.java.test.plugin 4 0 2023-08-30 16:56:02.252
!MESSAGE failed to search tests in: java
!STACK 1
Java Model Exception: Error in Java Model (code 969): <anonymous #1> {key=Lorg/eclipse/lemminx/extensions/contentmodel/XMLSchemaCompletionExtensionsTest$75658;} [in accept(org.eclipse.lemminx.services.XMLLanguageService) [in <lambda #1> [in customProtocolNamespaceSchemaLocationCompletionWhenCachingOn() [in XMLSchemaCompletionExtensionsTest [in XMLSchemaCompletionExtensionsTest.java [in org.eclipse.lemminx.extensions.contentmodel [in src/test/java [in org.eclipse.lemminx]]]]]]]] does not exist
	at org.eclipse.jdt.internal.core.JavaElement.newNotPresentException(JavaElement.java:550)
	at org.eclipse.jdt.internal.core.JavaElement.openWhenClosed(JavaElement.java:593)
	at org.eclipse.jdt.internal.core.JavaElement.getElementInfo(JavaElement.java:304)
	at org.eclipse.jdt.internal.core.JavaElement.getElementInfo(JavaElement.java:290)
	at org.eclipse.jdt.internal.core.Member.getFlags(Member.java:172)
	at org.eclipse.jdt.internal.junit.util.CoreTestSearchEngine.isAccessibleClass(CoreTestSearchEngine.java:64)
	at org.eclipse.jdt.internal.junit.launcher.JUnit5TestFinder.internalIsTest(JUnit5TestFinder.java:251)
	at org.eclipse.jdt.internal.junit.launcher.JUnit5TestFinder.findTestsInContainer(JUnit5TestFinder.java:221)
	at com.microsoft.java.test.plugin.searcher.JUnit5TestSearcher.findTestItemsInContainer(JUnit5TestSearcher.java:130)
	at com.microsoft.java.test.plugin.util.TestSearchUtils.findTestPackagesAndTypes(TestSearchUtils.java:168)
	at com.microsoft.java.test.plugin.handler.TestDelegateCommandHandler.executeCommand(TestDelegateCommandHandler.java:56)
	at org.eclipse.jdt.ls.core.internal.handlers.WorkspaceExecuteCommandHandler$1.run(WorkspaceExecuteCommandHandler.java:230)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
	at org.eclipse.jdt.ls.core.internal.handlers.WorkspaceExecuteCommandHandler.executeCommand(WorkspaceExecuteCommandHandler.java:220)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$4(JDTLanguageServer.java:612)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$59(JDTLanguageServer.java:1202)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)

I want to merge this, but we should really wait to confirm that the delegates commands are well behaved and don't result in report error, which result in spinning forever.