fix: authenticate LDAP via actual DN instead of normalized DN
Normalized DN is only for internal representation, not for
external communication, any communication to LDAP must be
based on actual user DN. LDAP servers do not understand
normalized DN.
fixes#19757
This change uses the updated ldap library in minio/pkg (bumped
up to v3). A new config parameter is added for LDAP configuration to
specify extra user attributes to load from the LDAP server and to store
them as additional claims for the user.
A test is added in sts_handlers.go that shows how to access the LDAP
attributes as a claim.
This is in preparation for adding SSH pubkey authentication to MinIO's SFTP
integration.
```
==================
WARNING: DATA RACE
Read at 0x0000082be990 by goroutine 205:
github.com/minio/minio/cmd.setCommonHeaders()
Previous write at 0x0000082be990 by main goroutine:
github.com/minio/minio/cmd.lookupConfigs()
```
Create new code paths for multiple subsystems in the code. This will
make maintaing this easier later.
Also introduce bugLogIf() for errors that should not happen in the first
place.
