testing framework: allow providers to reference run blocks

[liamcervante]

This PR allows provider configurations to reference run blocks inside testing files.

To make this possible, I've introduced a field in the TestSuiteRunner that tracks the providers required for each configuration that a test suite might require. This is so that we can now selectively hand providers over to each run block as required, instead of the previous approach which simply copied all the provider configurations across for every run block.

I also fixed a bug in the provider configuration logic that meant it wasn't properly raising diagnostics and giving bad error messages for problems within the provider configurations.

Fixes #34100
Fixes #34007

Target Release

1.7.0

Draft CHANGELOG entry

ENHANCEMENTS

• terraform test: Allow referencing run blocks from provider configurations in test files.

[github-actions]

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[github-actions]

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