Docs: Feedback for Security Realms

Page: https://github.com/hazelcast/imdg-docs/blob/v4.2/docs/modules/security/pages/security-realms.adoc

Based on user's feedback, configuring LDAP was quite problematic and the documentation didn't suffice. In particular, he would appreciate more detailed description of what which option does and what do you need to set.

I think we need to go through this chapter from the end-to-end perspective, perhaps review it together with the Support team.