Meta+LibUnicode: Move unicode_data helper to Meta/CMake

Moving this helper CMake file to the centralized Meta/CMake folder helps
to get a better grasp on what extra files are required for the build,
and what files are generated.

While we're at it, don't use add_compile_definitions for
ENABLE_UNICODE_DATA, which only needs to be seen by LibUnicode sources.

Meta/Azure/Caches.yml

@@ -36,13 +36,13 @@ steps:
   - ${{ if eq(parameters.with_unicode_caches, true) }}:
     - task: Cache@2
       inputs:
-        key: '"unicode_data" | Userland/Libraries/LibUnicode/unicode_data.cmake'
+        key: '"unicode_data" | Meta/CMake/unicode_data.cmake'
         path: $(Build.SourcesDirectory)/${{ parameters.build_directory }}/UCD
       displayName: 'UnicodeData Cache'
 
     - task: Cache@2
       inputs:
-        key: '"unicode_locale" | Userland/Libraries/LibUnicode/unicode_data.cmake'
+        key: '"unicode_locale" | Meta/CMake/unicode_data.cmake'
         path: $(Build.SourcesDirectory)/${{ parameters.build_directory }}/CLDR
       displayName: 'UnicodeLocale Cache'