Move definitions for magnification.dll to winBindings (#18958)
### Summary of the issue:
Screen curtain defined ctypes bindings to magnification.dll from the
Windows API.
### Description of user facing changes:
None.
### Description of developer facing changes:
Moved definitions to `winBindings.magnification`.
### Description of development approach:
Move definitions to `source/winBindings/magnification.py`. Remove from
`Magnification` class. Add deprecation handling code. Tidy definitions
to not use so many temporary definitions.
Note that these definitions use ctypes' function prototype syntax. This
was carried across from the old definitions. We plan to move to this
syntax anyway.
### Testing strategy:
Ran from source. Tried enabling temporary and regular screen curtain.
Tried importing deprecated symbols.
### Known issues with pull request:
None
