We already avoid system framework paths while looking for LDAP headers
to avoid issues.
Do the same while looking for LDAP libraries. This makes sure to find
the regular ldap library (`libldap.tbd`) instead of picking up
`ldap.framework` and let that seep into `libcurl.pc` with a full path.
This makes LDAP detection work on Apple as before introducing FindLDAP.
Follow-up to 49f2a23d50#15273Closes#15895
Make the Find modules set and return their respective `pkg-config`
module name(s) to the CMake build process, which then adds those
to the `Requires:` list.
Before this patch, `pkg-config` module names were maintainted in two
separate places. After this patch, they are maintained in the Find
modules for dependencies that have one (most do).
Re-align existing modules with this change: msh3, mbedtls, rustls.
These modules return their `pkg-config` module name only when
detected via `pkg-config`.
Follow-up to d511ec8b0a#15573Closes#15800
Move LDAP detection to its own Find module.
It supports `pkg-config` and the standard detection method used for
other dependencies, with version detection.
In curl CI it fixes LDAP detection in the OpenBSD job.
Closes#15273
