Rename resource files so JakartaMail and JavaMail can co-exist

[jmehrens]

Reported by https://github.com/jodastephen in jakartaee/mail-api#527 (comment)

That the content handlers from the old com.sun JakartaMail get mixed with the handlers from org.eclipse in the new JakartaMail which results in a ClassCastException.

We should consider renaming resources in META-INF:

1. javamail.charset.map -> jakarta.charset.map
2. javamail.default.address.map -> jakarta.charset.map
3. mailcap -> jakarta.mailcap
4. TODO update other resources that we probe for to use jakarta namespace.

This is something that should be considered for 2.1.X release.