[io-layer] Extract file (#4255)

[io-layer] Extract file (#4255)

* [io-layer] Merge io related headers

* [io-layer] Remove global variable _wapi_had_shut_down

* [io-layer] Inline io-portability.c file into io.c

* [io-layer] Inline locking.c file into io.c

* [io-layer] Inline posix.c file into io.c

* [file] Move metadata/file-io* files to metadata/w32file*

* [io-layer] Extract file functions

* [file] Remove overlapped parameter which is always NULL

* [file] Remove SECURITY_ATTRIBUTES parameter which is always NULL

* [file] Remove GET_FILEEX_INFO_LEVELS parameter which is always GetFileExInfoStandard

* [file] Replace ULARGE_INTEGER parameter type with guint64

* [file] Replace WIN32_FILE_ATTRIBUTE_DATA parameter type with MonoIOStat

* [file] Remove mono_w32file_create unused parameter tmplate

* [file] Fix win32 build