[test_reflective_loader] Don't add setUp/tearDown if not defined, and provide correct locations

[DanTup]

This makes the calls to setUpAll and tearDownAll conditional based on whether there are corresponding methods, so that there aren't phantom nodes in the IDE for all test classes.

It also adds missing locations, so that they navigate to the correct location when clicked.

Fixes Dart-Code/Dart-Code#5967
Fixes Dart-Code/Dart-Code#5950

While testing, I also noticed package:test is always adding a tearDownAll if there is a setUpAll - I've filed dart-lang/test#2608 about that.

[DanTup]

(cc @scheglov, this is low priority but I don't know if you get any notifications here since it's a mono repo)

[gemini-code-assist]

Code Review

This pull request is a great improvement. It conditionally adds setUpAll and tearDownAll calls, preventing phantom nodes in IDEs, and also provides correct locations for them. The refactoring of test running logic into a shared utils.dart file is a nice cleanup. The changes are well-tested. I've left a few minor comments regarding documentation to align with the project's style guide.

[mosuem]

@scheglov I think this is waiting for your review :)

[DanTup]

@scheglov ping :-)

[DanTup]

@scheglov thanks! Do you know what's with the bots? There are two actions that seem to be waiting (GH Actions Scan and Workflow Security Scan) but since it's been 18 hours since this was approved, I'm wondering if they are stuck.

[scheglov]

Yeah, I was waiting for bots, in case if they will start later; not landing yet.
But maybe I should say that I waited enough, and do it anyway :-)