ENH: Allow the use of type-aliases in the typing tests

[BvB93]

Mypys' string representation of certain types can get quite verbose, especially when larger Unions are involved.
Ideally we should be able to use aliases when running the reveal tests, allowing us to keep things a bit more compact:

numpy/numpy/typing/tests/data/reveal/arithmetic.py

Lines 84 to 86 in c004383

	reveal_type(c16 + c16) # E: numpy.complexfloating[numpy.typing._64Bit, numpy.typing._64Bit]
	reveal_type(c16 + f8) # E: numpy.complexfloating[numpy.typing._64Bit, numpy.typing._64Bit]
	reveal_type(c16 + i8) # E: numpy.complexfloating[numpy.typing._64Bit, numpy.typing._64Bit]

For further reference: there is currently a mypy issue with a similar request, but who know when/if
this will be implemented (python/mypy#9381).

[BvB93]

Another use case as encountered in #17843 and #17514: platform-specific types. Describing a dynamically assigned class with a static comment has proved somewhat troublesome:

import numpy as np

p: np.intp

# Can be either `numpy.signedinteger[numpy.typing._64Bit]` or `numpy.signedinteger[numpy.typing._32Bit]`
reveal_type(p)  # E: numpy.signedinteger[numpy.typing._