CRISP: remove usages of deprecated interfaces

Remove org.springframework.security.oauth2.client.OAuth2RequestAuthenticator and related deprecated usages.

For instance, org.onehippo.cms7.crisp.core.security.oauth2.client.CaseSensitiveBearerDelegatingOAuth2RequestAuthenticator implements deprecated OAuth2RequestAuthenticator.

For the resolution, see "OAuth 2.0 Migration Guide" for Spring Security 5 at https://github.com/spring-projects/spring-security/wiki/OAuth-2.0-Migration-Guide.

Also, deprecated org.springframework.security.oauth2.client.OAuth2RestTemplate is in the example documentation at
https://documentation.bloomreach.com/14/library/concepts/crisp-api/introduction.html
https://documentation.bloomreach.com/14/library/concepts/crisp-api/configuration/example-with-webdam-rest-api.html
https://documentation.bloomreach.com/14/library/concepts/crisp-api/configuration/example-with-marketo-rest-api.html
https://documentation.bloomreach.com/14/library/concepts/crisp-api/configuration/example-with-salesforce-rest-api.html