Improve test output handling

[hbenl]

Test adapters can send output from tests to Test Explorer and this converter will pass those messages to the native testing API using vscode.TestRun.appendOutput(). But I can't find these messages anywhere in the UI, only the messages sent to vscode.TestRun.failed() or vscode.TestRun.errored().
Furthermore, output sent to Test Explorer can be associated with a running test, but the native testing API doesn't seem to support that (except for error messages). This can be very useful because you don't have to wade through all messages from a test run to find the messages from a particular test.

[connor4312]

appendOutput strings are shown in the Test Output, which can be seen using the Test: Show Output command, also accessible via the ctrl+; ctrl+o chord or via the "terminal" icon in the test explorer view.

output sent to Test Explorer can be associated with a running test, but the native testing API doesn't seem to support that (except for error messages

That's requested in microsoft/vscode#129201 and should come this month. Closing this as a dupe of that one 🙂