[libclang/python] Return actual C types from libclang functions instead of Python bool (llvm#166446)

In the previous implementation, 43 libclang functions are registered in
FUNCTION_LIST with return type ctypes.c_bool. However, none of these
functions actually return a C bool type; instead, they return unsigned
or signed integers (unsigned int / int) on the C side.

Although ctypes automatically casts nonzero integers to True and zero to
False, this implicit conversion hides the "true" c-return type.

This PR updates those functions to use their proper “native” ctypes
return types (c_uint or c_int) and updates the corresponding Python
convenience wrappers to explicitly cast their results using the bool
constructor.

As a side effect, the related `# type: ignore` annotations have been
removed, as they are no longer necessary.

Some libclang functions are used directly without any intermediate
Python wrapper. These functions (`clang_equalCursors`,
`clang_equalLocations`, `clang_equalRanges`, `clang_equalTypes`,
`clang_File_isEqual`, and `clang_isFileMultipleIncludeGuarded`) are now
explicitly cast to bool at their call sites. Note that
`clang_isFileMultipleIncludeGuarded` is never called in the binding.

Thix fix llvm#164915.

Author: TApplencourt