arrow

ARROW-18173: [Python] Drop older versions of Pandas (<1.0) (#14631)

This PR tries to make changes to drop older versions of pandas and support versions >= 1.0.0.

The changes will have to be done in:
- [x] the official documentation (pandas version support)
- [x] the CI jobs supporting older pandas versions
- [x] https://github.com/apache/arrow/blob/master/python/pyarrow/pandas-shim.pxi
- [x] tests that are specifically testing features on older versions of pandas

Lead-authored-by: Alenka Frim <frim.alenka@gmail.com>
Co-authored-by: Alenka Frim <AlenkaF@users.noreply.github.com>
Co-authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>