Add Twitter/X to CommonOAuth2Provider

[rwinch]

To simplify configuring applications to authenticating using Twitter / X v2 API we should add Twitter/X to the CommonOAuth2Provider.

spring.security.oauth2.client.registration.x.scope=users.read,tweet.read

spring.security.oauth2.client.provider.x.authorization-uri=https://x.com/i/oauth2/authorize
spring.security.oauth2.client.provider.x.token-uri=https://api.x.com/2/oauth2/token
spring.security.oauth2.client.provider.x.user-info-uri=https://api.x.com/2/users/me
spring.security.oauth2.client.provider.x.user-name-attribute=username