BUG: MaskedArray __eq__ wrong for masked scalar, multi-d recarray

In the process of trying to fix the "questionable behaviour in
`MaskedArray.__eq__`" (gh-8589), it became clear that the code was
buggy. E.g., `ma == ma[0]` failed if `ma` held a structured dtype;
multi-d structured dtypes failed generally; and, more worryingly,
a masked scalar comparison could be wrong:
`np.ma.MaskedArray(1, mask=True) == 0` yields True.

This commit solves these problems, adding tests to prevent regression.
In the process, it also ensures that the results for structured arrays
always equals what one would get by logically combining the results
over individual parts of the structure.

0 files changed, 0 insertions, 0 deletions