BUG: use internal linkage (static variables) in move.c
move.c declared global variables without explicitly declaring them static, so
they had global visibility. This meant that if you linked against a shared
object that provided the same symbols, the wrong data would be read. In
particular: linking to libgtk, which provides the symbol 'methods', would cause
an import error of pandas.util._move.

- [x] closes #19706
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry
