Add support for advanced test lifecycle callbacks - setUpAll

[bartekpacia]

Targeted at #1503.

See investigation conducted in #1741.

[bartekpacia]

Patrol's test bundling feature offloads scheduling&execution of tests to package:test. How it works is that we always execute all the tests, but only the one is requested and runs, and the rest is skipped (i.e. their body is executed but exits early). This behavior implies being able to access currentTest from within testWidgets, setUp and tearDown body, so we can if currentTest == requestedTest and decide whether to skip or execute it.

However, currentTest is not available inside setUpAll and tearDownAll body callbacks, so this exact approach won't work.

I think a workaround based on using parentGroup should work. See gist.

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currentTest = Invoker.current!.liveTest.individualName
parentGroup = Invoker.current!.liveTest.groups.last.name

[bartekpacia]

When should the setUpAll callbacks be run? The obvious answer is "before its tests start running". This means that Dart side has to know which Dart setUpAll callbacks have already run, and which not.

This is a problem, because currently, the only synchronization point between instrumentation app and app under test is markPatrolAppServiceReady() and listDartTest(). Both of them happen too late, after all tests have been executed, after all setUpAlls have been called.

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I made a playground where I'm testing how to bend package:test API to our use case.

[bartekpacia]

Plan

To discover setUpAlls, all tests must run. This currently cannot be done during the inital run, because Dart tests only run after runDartTest() is called.

To fix that, behavior of Dart tests must differ between the initial run and normal runs. Currently this behavior is mostly the same:

1. App under test starts
2. patrol_test_explorer test runs, subsequent tests DO NOT RUN
3. Once patrol_test_explorer finishes, instrumentation calls listDartTests()
4. [Only in normal run] Once listDartTests() finishes, instrumentation calls runDartTest()

But to collect setUpAlls, this would have to happen:

1. App under test starts
2. patrol_test_explorer test runs, subsequent tests RUN but are SKIPPED
3. Once patrol_test_explorer finishes, instrumentation calls listDartTests()
4. [Only in initial run] Once listDartTests() finishes, instrumentation calls listDartLifecycleCallbacks()
5. [Only in normal run] Once listDartTests() finishes, instrumentation calls runDartTest()

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