Update the slapd image base to use Debian 11 or bullseye
and update default build arguments.

Update the base Debian image used for the slapd images.

Refactored the Dockerfiles and related
tooling to leverage Docker multi-stage build
functionality. Also updated base containers
to pick up later releases of Apache HTTP Server,
PHP, Shibboleth SP, and mod_auth_openidc.

As part of refactor of slapd moved the entrypoint script from
slapd-base to slapd and created Dockerfile for slapd to put it
into plase.

As part of refactor of the slapd images move
comanage-registry-slapd to comanage-registry-slapd-base.

Moved most of the slapd entrypoint script to a bash package
so that it is more reuseable with downstream Docker packages.

Add voPerson LDAP schema to image and refactor the slapd entrypoint
script so that additional schemas are checked for and added
if necessary during each start. Additionally the TLS configuration
is also managed during each start instead of only once at
bootstrap. Also added synprov module to bootstrap.