Support UnboundID LDAP SDK 7.0

[wilkinsona]

https://github.com/pingidentity/ldapsdk/releases/tag/7.0.0

The devil will be in the details, but looking at the release notes, the only obviously breaking change is dropping support for Java 7. As such, for Spring's user base, 7.0 may be more of a minor release in terms of upgrade pain.

[marcusdacoregio]

I'll schedule this for the next major release since we don't typically upgrade to a major version during our minor releases. I've tested Spring Security 6.4 against UnboundID 7.0.1 and all tests passes.

If the plans change I'll update here.