[13.x] Rename CheckClientCredentials middleware

[hafezdivandari]

This PR corrects the naming of the CheckClientCredentials and CheckClientCredentialsForAnyScope middlewares. As mentioned in this comment and this issue, the current naming is confusing and does not accurately reflect the functionality of these middlewares:

• The CheckClientCredentials class has been renamed to CheckToken, as it does not check client credentials but instead verifies whether the token is valid and has all the specified scopes.
• The CheckClientCredentialsForAnyScope class has been renamed to CheckTokenForAnyScope, as it does not check client credentials but verifies whether the token has any of the specified scopes.
• The CheckCredentials abstract class has been renamed to ValidateToken, as it does not check credentials but rather parses and validates the bearer token.

Summary

• CheckClientCredentials -> CheckToken
• CheckClientCredentialsForAnyScope -> CheckTokenForAnyScope
• CheckCredentials -> ValidateToken

Usage

Refer to the updated docs: