Remove reexported Resolver validation APIs

[PhilippGackstatter]

Description of change

Remove the reexported Resolver APIs that re-expose functionality from CredentialValidator and PresentationValidator. The latter APIs should be used instead.

Resolving and validating is slightly more hands-on now as a result, but reduces the Resolver's API surface and therefore complexity significantly. It also gives a better decoupling of resolution and validation, especially for handling errors that occur in either of those processes. The resolver Error also no longer has to re-export the validation errors, making it simpler too.

Overall this should result in less complexity for the user as well as the maintainers with not much impact on the API as is evident by the updated examples.

This also updates some examples to use the new JWT-based APIs, since this PR is part of a larger effort to remove the old Validators in favor of the new JWT-based ones.

Links to any relevant issues

part of #1103

Type of change

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• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix

How the change has been tested

Updated examples and ran them successfully.

Change checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes