Meson doesn't handle `limited_api_suffix = None` from `python_info.py`

[mgorny]

Describe the bug
Noticed this while working on #14657.

limited_api_suffix can technically be None:

meson/mesonbuild/scripts/python_info.py

Lines 95 to 107 in 5555027

	limited_api_suffix = None
	if sys.version_info >= (3, 2):
	try:
	from importlib.machinery import EXTENSION_SUFFIXES
	limited_api_suffix = EXTENSION_SUFFIXES[1]
	except Exception:
	pass
	# pypy supports modules targeting the limited api but
	# does not use a special suffix to distinguish them:
	# https://doc.pypy.org/en/latest/cpython_differences.html#permitted-abi-tags-in-extensions
	if is_pypy:
	limited_api_suffix = suffix

Though admittedly I don't know of any real life use case when this would happen. However, if it does, Meson crashes when trying to build limited API code:

Traceback (most recent call last):
  File "/home/mgorny/git/meson/mesonbuild/mesonmain.py", line 193, in run
    return options.run_func(options)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/msetup.py", line 392, in run
    app.generate()
  File "/home/mgorny/git/meson/mesonbuild/msetup.py", line 194, in generate
    return self._generate(env, capture, vslite_ctx)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/msetup.py", line 251, in _generate
    intr.run()
  File "/home/mgorny/git/meson/mesonbuild/interpreter/interpreter.py", line 3049, in run
    super().run()
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/interpreterbase.py", line 178, in run
    self.evaluate_codeblock(self.ast, start=1)
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/interpreterbase.py", line 203, in evaluate_codeblock
    raise e
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/interpreterbase.py", line 195, in evaluate_codeblock
    self.evaluate_statement(cur)
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/interpreterbase.py", line 215, in evaluate_statement
    return self.method_call(cur)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/interpreterbase.py", line 565, in method_call
    res = obj.method_call(method_name, args, kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/baseobjects.py", line 81, in method_call
    return method(args, kwargs)
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/decorators.py", line 103, in wrapped
    return f(*wrapped_args, **wrapped_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/decorators.py", line 237, in wrapper
    return f(*nargs, **wrapped_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/interpreterbase/decorators.py", line 556, in wrapper
    return f(*wrapped_args, **wrapped_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mgorny/git/meson/mesonbuild/modules/python.py", line 223, in extension_module_method
    split, target_suffix = target_suffix.rsplit('.', 1)
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'rsplit'

test cases/unit/125 python extension/meson.build:10:3: ERROR: Unhandled python exception

    This is a Meson bug and should be reported!

To Reproduce

project('python extension', 'c')

py = import('python').find_installation()

py.extension_module(
    'foo_stable', 'foo.c',
    install: true,
    limited_api: '3.10',
)

(foo.c can be empty)

To reproduce, I've used PyPy, but removed the limited_api_suffix = suffix fallback

Expected behavior
I think Meson should throw an explicit error that limited API is not supported.

system parameters

• Is this a cross build or just a plain native build (for the same computer)? Native.
• what operating system: Gentoo Linux amd64
• what Python version are you using: PyPy3.11 7.3.19
• what meson --version: 1.8.99 (5555027)
• what ninja --version if it's a Ninja build: n/a