Support for specification-compliant verification method type JsonWebKey2020

[UMR1352]

Description of change

Support for JWK-based verification has long been added to the library but under a non-standardized type - i.e. JsonWebKey. This PR solves this issue by making the already implemented method spec-compliant by changing the method's type to JsonWebKey2020 and deprecating the previous type.

Links to any relevant issues

Closes #1366

Type of change

• 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

Describe the tests that you ran to verify your changes.
Ran linter and all tests.

Change checklist

• 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