outpost/ldap: Compare

**Is your feature request related to a problem? Please describe.**
When using Authentik's LDAP Outpost to secure an apache server (mod_authnz_ldap), only `Require valid-user` constraints are functional.
Any constraint more complicated such as a group membership check is currently not possible, due to the ldap outpost not supporting the Compare operation.

**Describe the solution you'd like**
Authentik's LDAP Outpost should support the compare message type.

**Describe alternatives you've considered**
mod_auth_oidc is not useful here; common subversion clients such as Tortoise SVN and the svn command unfortunately do not support web-based authentication. (adding this to the list of reasons to prefer git to svn, as git does support web-based auth)

**Additional context**
A simple repro with ldapcompare:
```sh
# ldapcompare -H ldap://my_ldap_outpost:3389 -D ${ldapsearch_user} -w ${ldapsearch_password} ${ldapsearch_user} memberOf:ldap-search
Compare Result: Insufficient access (50)
Additional info: Insufficient Access Rights
UNDEFINED
```

I have a [proof-of-concept that implements Compare](https://github.com/Nopey/authentik/blob/fb8a807a48dc322732c233b9a76d746f2cc1c71d/internal/outpost/ldap/search.go#L90-L137) by calling Search and using beryju/ldap's filtering funcs (note: uses a [patched version of beryju/ldap](https://github.com/Nopey/go-ldap/tree/server_compare_test) to expose needed fields)

Discord link to the support channel, where I posted while exploring this: https://discord.com/channels/809154715984199690/1170914395472277584