Add missing _winapi functions (RustPython#7185)

* Add missing _winapi functions and fix WinHandle int conversion

Add 13 functions: ReadFile, SetNamedPipeHandleState, CreateFileMapping,
OpenFileMapping, MapViewOfFile, UnmapViewOfFile, VirtualQuerySize,
CopyFile2, ResetEvent, CreateMutex, OpenEventW, LoadLibrary,
_mimetypes_read_windows_registry.

Add constants: INVALID_HANDLE_VALUE, FILE_MAP_READ/WRITE/COPY/EXECUTE.

Change WinHandle integer type from usize to isize so negative values
like INVALID_HANDLE_VALUE (-1) can be passed from Python.

* Align _winapi module with CPython

- Rename winapi.rs to _winapi.rs with #[path] attribute
- Rename CreateMutex to CreateMutexW
- Add missing constants: ERROR_ACCESS_DENIED, ERROR_PRIVILEGE_NOT_HELD,
  PROCESS_ALL_ACCESS, 10 STARTF_ constants, LOCALE_NAME_SYSTEM_DEFAULT,
  LOCALE_NAME_USER_DEFAULT, COPY_FILE_DIRECTORY
- Fix OpenMutexW return type and ReleaseMutex param type to use WinHandle

* Fix ReadFile/WriteFile overlapped keyword argument

Use FromArgs structs so overlapped parameter can be passed as
a keyword argument (overlapped=True), matching the CPython API.

* Remove extra constants and LoadLibrary not in CPython _winapi

Remove 19 constants (WAIT_ABANDONED, CREATE_ALWAYS, CREATE_NEW,
OPEN_ALWAYS, TRUNCATE_EXISTING, FILE_ATTRIBUTE_NORMAL, 8 FILE_FLAG_*,
3 FILE_SHARE_*, NMPWAIT_NOWAIT, NMPWAIT_USE_DEFAULT_WAIT) and
LoadLibrary function that are not present in CPython's _winapi module.

* Fix utf8_mode default to 0 and add PYTHONUTF8 env var support

Default utf8_mode was incorrectly set to 1, causing text-mode
subprocess to always decode as UTF-8 instead of locale encoding.
Changed default to 0 to match CPython 3.13 behavior on Windows.
Added PYTHONUTF8 environment variable handling with -X utf8 override.

* Fix CopyFile2 to raise proper OSError subclass

Use std::io::Error::from_raw_os_error instead of vm.new_os_error so
that winerror attribute is set and errno-to-exception mapping works
(e.g. ERROR_ACCESS_DENIED → PermissionError).

* Fix syntax_non_utf8 test to not depend on locale encoding

Use explicit encoding='latin-1' so the test works regardless of
the system locale (e.g. C/POSIX locale uses ASCII by default).

Author: youknowone

.cspell.json

@@ -147,6 +147,7 @@
     // "stat"
     "FIRMLINK",
     // CPython internal names
+    "PYTHONUTF",
     "sysdict",
     "settraceallthreads",
     "setprofileallthreads"