DEP: Speed up WarnOnWrite deprecation in buffer interface

When a buffer interface does not request a writeable buffer,
simply pass a read-only one when the warn on write flag is set.

This is to give an easier way forward with avoiding the deprecation
warnings: Simply do not ask for a writeable buffer.

It will break code that expects writeable buffers but does not
ask for them specifically a bit harder than would be nice.
But since such code probably should ask for it specifically, this
is likely fine (an RC release has to find out).

The main reason for this is, that this way it plays very will with
cython, which requests writeable buffers explicitly and if declared
`const` is happy about read-only (so that using `const` is the best
way to avoid the warning and makes code cleaner).

Closes gh-13929, gh-13974

BUG: Handle weird bytestrings in dtype()

 * Explicit check for negative type value in PyArray_DescrFromType
 * PyArray_DescrConverter casts to unsigned char to match python bytes
 * Add some tests

The code path in scalarapi.c which checks dtype on one inheriting
from np.void is especially awkward and was completely untested
previously. So I am not sure we should even support it at all.

Closes gh-12982, gh-3614, and gh-12751

We do not want to allocate 0 bytes (since it is not well defined),
normally nbytes is 0 if the array is empty. But in case also the
descriptor element size is empty, use 1 byte.

When the base is not an array (or generally when the flag of the base
array was toggled), it is OK to allow setting the writeable flag to
True, as long as any ancestor (especially the last one) is writeable.

This commit also slightly change the behaviour of the base attribute. 

---

* ENH: Deprecate writeable broadcast_array

* ENH: Make writeable flag enabling more reliable for non-array bases

When the base is not an array (or generally when the flag of the base
array was toggled), it is OK to allow setting the writeable flag to
True, as long as any ancestor (especially the last one) is writeable.

* Update doc/release/1.17.0-notes.rst

Co-Authored-By: Sebastian Berg <sebastian@sipsolutions.net>

* Update doc/release/1.17.0-notes.rst

Co-Authored-By: Sebastian Berg <sebastian@sipsolutions.net>

* Update numpy/lib/tests/test_stride_tricks.py

Co-Authored-By: Sebastian Berg <sebastian@sipsolutions.net>

* Update numpy/core/tests/test_multiarray.py

Co-Authored-By: Sebastian Berg <sebastian@sipsolutions.net>

* DOC: improve warning (from review)

BUG: Fix memory leaks in dtype constructor code