SpringBoot Add resource hints for default MessageSource properties file locations

This only registers the default locations, not the one users can provide via 'spring.messages.basename'.

This is similar to the approach taken for schema.sql and data.sql in class SqlInitializationScriptsRuntimeHints.

Closes gh-36137

Comment From: wilkinsona

@beckermarc thanks very much for making your first contribution to Spring Boot.

Comment From: beckermarc

thanks for merging! :)