Add AOT support for the EntryPoint property for UnmanagedCallersOnly. (#44809)
* Change mono_reflection_create_custom_attr_data_args_noalloc () so it returns the beginning of the metadata string so its length can be computed.
* Add AOT support for the EntryPoint property for UnmanagedCallersOnly.
Fixes https://github.com/dotnet/runtime/issues/44803.
* Update src/mono/mono/mini/driver.c
Co-authored-by: Aleksey Kliger (λgeek) <akliger@gmail.com>
Co-authored-by: Aleksey Kliger (λgeek) <akliger@gmail.com>