Remove unused CMake modules (#16452)

* Remove unused CMake modules

FindAlienWx.cmake and FindPerlEmbed.cmake came over from the Slic3r Perl
build. Nothing calls find_package(AlienWx) or find_package(PerlEmbed).

LibFindMacros.cmake was only included by those two modules.

bin2h.cmake lost its last caller when the avrdude sources were removed
in e6fcbfae07.

* ci: build changes under cmake/

The Build all path filters did not include cmake/, so a change to a
find module or to ClangClShowIncludes.cmake ran no build on a pull
request or on a push to main.

.github/workflows/build_all.yml

@@ -8,6 +8,7 @@ on:
     paths:
      - 'deps/**'
      - 'deps_src/**'
+     - 'cmake/**'
      - 'src/**'
      - '**/CMakeLists.txt'
      - 'version.inc'
@@ -31,6 +32,7 @@ on:
     paths:
      - 'deps/**'
      - 'deps_src/**'
+     - 'cmake/**'
      - 'src/**'
      - '**/CMakeLists.txt'
      - 'version.inc'