DOC: Template Timestamp & NaT docstrings

[mroeschke]

Currently some NaT's method docstrings directly mirror Timestamp's method docstrings via copy and pasting.

e.g.

pandas/pandas/_libs/tslibs/timestamps.pyx

Lines 646 to 650 in 4f71755

	"""
	Timestamp.fromtimestamp(ts)
	timestamp[, tz] -> tz's local time from POSIX timestamp.
	"""

pandas/pandas/_libs/tslibs/nattype.pyx

Lines 368 to 372 in 4f71755

	"""
	Timestamp.utcfromtimestamp(ts)
	Construct a naive UTC datetime from a POSIX timestamp.
	"""

We don't want to import Timestamp into nattype.pyx to avoid a circular import. Ideally we should template the docstrings of both Timestamps and NaT methods to avoid this copy pasting.

[jbrockmendel]

I don’t think this is going to be viable anytime soon. Maybe as a second-best we could have tests that they are in sync?

[mroeschke]

I think we already have tests that they are in sync, but this is just a nice to have for the future.

[jbrockmendel]

labelled as blocked, as i dont think anything Appender-like will play nicely with cython

[mroeschke]

Since we have a unit test ensuring these are the same. I think that's good enough so closing