Remove all WITH_* flags from _imaging.c and other flags

[homm]

Rationale

• The value of these flags is questionable. I don't see real use cases.
• Python code is not aware of these flags. After compiling without some of them, Pillow functionality is not guaranteed.

[homm]

I've tried to measure performance penalty for saving state.

Empty function call:

In [2]: %timeit Image.core.test_threading()
64.1 ns ± 0.842 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

With ImagingSectionEnter/ImagingSectionLeave:

In [6]: %timeit Image.core.test_threading()
109 ns ± 0.951 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

[wiredfool]

LGTM, This probably deserves a changelog entry -- as technically it's possible that people have been editing this.

[radarhere]

Just for clarity - you're removing 'Kevin Cazabon' presumably because the code has been modified over time?

[homm]

If the reason were due to modifications over time, I would have included additional names accordingly. The actual reason is that I was unsure of the specific value this information provides in the comments. However, if this is important, I can revert the change.

[hugovk]

Please mention this in the release notes: https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/11.0.0.rst

[homm]

@hugovk @wiredfool
Release notes added