Parameter increasing LDAP sync

**Describe your question/**
Is there a way to increase the ldap sync? I tried to tweak it by setting the PAGE size, but that only leads to a minor change.

The following is the measured performance when syncing around 5000 users of a 98000 ad directory.
It shows how many users are synced per second in average and the configured `AUTHENTIK_LDAP__PAGE_SIZE`.

- 9,50 users/s - 50
- 9,58 users/s - 500
- 9,67 users/s - 1000
- 9,40 users/s - 2000
- 8,98 users/s - 5000

That leads to a sync time close to 3 hours, which is not that applicable for regular syncs (e.g. Passwords etc). Would be nice to be able to increase that time with more hardware resources or some parameters.

Also I think it would be nice to tweak the sync process be only syncing changed values (e.g. using `whenChanged` of ad). I know that it also gets updated, when the user logs in, but I should decrease the number of entries to sync. At least that`s the way I think to do a cron job to sync entries.

Since I already posted several issues, I just wanted to say you did a great job with Authentik. :)

**Relevant infos**
- separate PostgreSQL db (pgpool)

**Screenshots**
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**Logs**
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**Version and Deployment (please complete the following information):**

- authentik 2023.8.3
- docker compose version

**Additional context**
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