Adding authentication methods display name for the client authenticators

[ChinthakaJ98]

Purpose

This PR updates the getSupportedClientAuthenticationMethods() method in the OAuthClientAuthenticator so that it could return both supported authentication mechanisms by the authenticator and their respective display names which could be displayed in the console UI.

[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/6769241344

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PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/6769241344
Status: failure

[ChinthakaJ98]

Integration tests fail here because getSupportedClientAuthenticationMethods method [1] is updated in the OAuthClientAuthenticator interface and this needs to be updated in both MTLS and PrivateKey JWT authenticators as well. These authenticators has been updated accordingly in the PR [2].
[1] https://github.com/wso2-extensions/identity-inbound-auth-oauth/pull/2243/files#diff-0b5655c78a741a01d6e1fac11bd4d3bf5b4da7a598fbd11c054b82bac6bcfe7aR76
[2] wso2-extensions/identity-oauth-addons#117