Issues from `TODO`s in `timestamps.pyi`, `timedeltas.pyi` and `orc.pyi`

[cmp0xff]

This issue is created so that TD003 can be complied to.

orc.pyi

• In read_orc, we need to type the filesystem with the correct pyarrow types.

timestamps.pyi

• We need to test Timestamp - np.timedelta64.
• We need to check if tz_localize could return NaT or not.
• We need to check if round/floor/ceil could return NaT or not.

timedeltas.pyi

• We need to check if round/floor/ceil could return NaT or not.