Upgrade Unboundid to 6.0.6

[mdiskin]

Expected Behavior

Support latest improvements and better defaults for security protocols such as removing SHA1 prefering TLS1.3. Also for embedded you no longer need to enable the operational attriubutes.

https://nawilson.com/2021/05/28/unboundid-ldap-sdk-for-java-6-0-0/

Current Behavior

Works but falling a number of major versions behind which can be an audit concern.

Context

The initial request was related to bug (not unboundid but in the autoconfig) in embedded ldap springboot
spring-projects/spring-boot#23030

[jzheaux]

Before marking this at 6.x, let's see there is a way to have 5.6.x support both UnboundId 4 and the latest, similar to what was done with #9095. This way, 5.6.x can have the latest UnboundId support while allowing folks to stay on UnboundId 4.x if needed.

[rwinch]

For this issue we should also ensure old unboundid support is removed in 6.0.x

[marcusdacoregio]

Unboundid 6.x already works with Spring Security 5.x, users can opt into it if they want. Spring Boot also uses Unboundid 6.x in 2.7.