feat: test context improvements

[cylewitruk]

Description

Pulled this out of my tx-signer branch to help reduce its size/conflicts (I use these changes there).

This PR comes with a number of improvements to how we test using the Context. It was starting to get a little messy with the different Context testing variants -- this addresses that and makes it consistent across the project.

Changes

• Adds a typestate builder for the TestContext which provides convenience methods for using mocks etc., as well as allowing you to provide your own concrete impls.
• Adds an automock for StacksInteract.
• Removed TestSignerContext, NoopApiClient, etc. and refactored everything to use the TestContext and its builder methods.
• Refactored tests to use TestContext and mocked clients instead of NoopApiClient.

Testing Information

Nothing special as this is test code itself.

Checklist:

• I have performed a self-review of my code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[matteojug]

Nice!