Support explicitly disposing test dependencies

Traditionally, we don't use dependency injection for objects that need to be explicitly disposed (e.g. rest clients that we want to stick around for all tests to reuse.) They are handled as part of the unit test method lifecycle using unit test setup/teardown. This works fine in _most_ cases, but has always been kinda shaky as it can easily break the TestFramework concept of not hiding dependencies away.

_However_, we recently ran into a situation migrating a project from Selenium to Playwright, and had issues with how that project was managing disposable objects. Hooking playwright into the existing framework would involve a lot of effort, but Injecting the playwright disposables into DI doesn't properly work as we declare test dependencies as singletons so it doesn't reliably get cleaned up at the end of a test (playwright's instance is static, that may be the difficulty here.)

Consideration: For Playwright specifically, the parent Playwright object is okay to leave around for the entire test run, but we really want to destroy the browser context (and possibly the browser itself) between each run so that we're NOT just adding more open browsers on longer test runs.

Some possible fixes:
- Do nothing. Create a finally block to dispose the context (and possibly browser)
- Pro: It's easy and visible
- Con: for new projects someone will need to know to do this
- Possible mitigation:
- Update documentation and provide an example in the Examples project
- Write an analyzer that throws an informational message (already have other items that would be good for an analyzer, e.g. test blocks with no execute method.)
- Change or add Add(Async)TestBlock and Add(Async)FinallyBlocks that use a scoped lifetime.
- Pro: automagically handled
- Con: Could be unintentional behavior changes if we update existing methods, or would require someone to know the difference between scoped and singleton lifetimes (or what's disposable and what isn't) if we add new methods, which breaks the concept of not requiring and automated tester to know those specifics
- Possible mitigation:
- Four unique methods, something like Add(Async)DisposableTest(Finally)Block
- Just change the existing methods to use scoped instead of singleton
- Update the TestCase behavior to search through the container for any singletons that implement IDisposable and explicitly call them before going into the logic to throw any exceptions that occurred

Start by reviewing the Add(Async)TestBlock and Add(Async)FinallyBlocks options, then examine the TestCase behavior described in the issue. A completed change should establish and document one disposal approach that reliably cleans up per-test Playwright browser contexts and possibly browsers without hiding dependencies.

Scritto dal modello di indicizzazione a partire dal testo della issue.