Fix Windows build with pyproject.toml

[nulano]

Continuation of #7190.
Closes #7190.

Two changes:

• Use pip install -C raqm=vendor -C fribidi=vendor . instead of calling setup.py directly.
• Extract the environment setup into a separate script:
  • selecting wheel vs install and passing through pip flags cannot be easily done via a batch script,
  • this change (very slightly) speeds up compilation locally and on AppVeyor,
  • it will enable build caching simplifications after Removed support for 32-bit #7228 is merged.

[hugovk]

The egg format is newly deprecated on PyPI:

• https://peps.python.org/pep-0715/

I know we're not uploading these, but do we need them here?

Suggested change

	- path: pillow\*.egg
	name: egg

(Non-blocking for merge.)

[hugovk]

Eggs can wait, let's merge so everything is ready in time for tomorrow's build. 🥚🚀

Thanks!