BUG/TST: Add searchsorted tests
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

xref: https://github.com/pandas-dev/pandas/issues/32845
LGTM Carried over to https://github.com/pandas-dev/pandas/pull/32764 since there's overlap