Only validate IDs for PF resources

[iwahbe]

This PR is best reviewed commit by commit:

• eb9cc3c38c47fdfbeb15f056fced769eedcaa354 restricts ID validation to PF based resources. SDK based resources all have an implicit ID field and so don't need this check.
• 5754d071ba41edf01b283fae82143b5cf7ce36a8 moves the various provider validation functions into 1 main function: checkProvider. This ensures that every entry point can just call checkProvider. Previously we had two validation functions and we didn't always call both of them.
• 9641d85d4f16ee9e205b3aaabc6f8c17c038cbc2 refactors checkProvider and it's sub-functions into their own internal package. We do this to prevent directly calling the non-primary function.
• df23bf25511ca4a638453c6bb8ce8c83da416d23 adds some tests to the check in general, and the new behavior introduced in eb9cc3c38c47fdfbeb15f056fced769eedcaa354 in particular.

Fixes https://github.com/pulumi/pulumi-terraform-bridge/issues/2030

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 53.84615% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 63.24%. Comparing base (9cf2ede) to head (875c5c0). Report is 2 commits behind head on master.

Files	Patch %	Lines
pf/tfgen/main.go	0.00%	7 Missing :warning:
pf/internal/check/not_supported.go	50.00%	1 Missing and 1 partial :warning:
pf/tfgen/gen.go	0.00%	1 Missing and 1 partial :warning:
pf/internal/check/checks.go	92.30%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2029 +/- ## ========================================== + Coverage 61.10% 63.24% +2.14% ========================================== Files 334 333 -1 Lines 44940 37387 -7553 ========================================== - Hits 27459 23647 -3812 + Misses 15960 12213 -3747 - Partials 1521 1527 +6 ```

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[iwahbe]

It's not entirely clear to me that this needs to be in an internal package.

I'm not sure what you mean. Are you suggesting that it shouldn't be a package or that it shouldn't be internal?

Is it not sufficient to export Provider (and Provider only) if we have a new check package?

We do export Provider (and Provider only), but we only export them for tfgen. We don't want end users to be calling these functions. We don't have any backwards compatibility guarantees on names or signatures.

[guineveresaenger]

I see, you are saying end users should not be calling check.Provider() at all either.

I don't have a particularly strong feeling here; I would've left it at tfgen.checkProvider but usage wise internal makes sense too. Feel free to resolve.

[iwahbe]

Waiting on API token limits to get to a green CI and merge.