build: replace Perl ExtUtils::MakeMaker with pure CMake install

MakeMaker was only used to copy .pm files — no XS compilation, no binary
linking, no dependency resolution. Its hardcoded "Makefile" output name
conflicts with cmake's generated Makefile for in-source builds, and using
FIRST_MAKEFILE=MakefilePerl causes thousands of "uninitialized value"
warnings because MM.pm stats the wrong file.

Replace with native CMake install(DIRECTORY ... FILES_MATCHING PATTERN
"*.pm") directives. Perl module install path is auto-detected at configure
time via `perl -MConfig` (vendorlib on Linux, sitelib on FreeBSD),
overridable with -DZM_PERL_INSTALL_PATH=<path>.

What's removed:
- ExtUtils::MakeMaker as build dependency
- Three perl+make subprocesses at build time (zmperlmodules,
  zmonvifmodules, zmonvifproxy build targets)
- ~6000 auto-generated man3 pages from WSDL stubs
- MakeMaker scaffolding: Makefile.PL, MANIFEST, META.yml, Changes,
  README, and t/ZoneMinder.t test stub

What's preserved:
- configure_file() for .pm.in templates (same behavior)
- ZM_PERL_SEARCH_PATH (independent mechanism, unchanged)
- Section 8 man pages for .pl scripts (Pod2Man.cmake, unaffected)
- DESTDIR support (CMake install() handles natively)
- Installed file paths (perl -MConfig returns same paths MakeMaker used)

Verified: 3102 .pm files installed, 0 .pm.in files, 0 .3pm man pages,
no @VERSION@ markers in generated files, DESTDIR and user override work.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

distros/beowulf/libzoneminder-perl.install

@@ -1,2 +1 @@
-usr/share/man/man3
 usr/share/perl5

distros/ubuntu2004/libzoneminder-perl.install

@@ -1,2 +1 @@
-usr/share/man/man3
 usr/share/perl5