The helpers added by:
* commit 37bc3400cd (CMakePackageConfigHelpers: Add
generate_apple_platform_selection_file(), 2023-11-03)
* commit 4ac5a2f866 (CMakePackageConfigHelpers: Add
generate_apple_architecture_selection_file(), 2023-12-19)
were worded in terms of including package configuration files, but the
actual functionality is to include files *from* package configuration
files. The included files do not themselves need to be usable as
package configuration files.
Rename the options and clarify the documentation accordingly.
Issue: #25262
Issue: #25516
The template added by commit 37bc3400cd (CMakePackageConfigHelpers: Add
generate_apple_platform_selection_file(), 2023-11-03) is specific to
Apple platforms. Give it an Apple-specific name.
