feat: stricter selector parsing, refactor to platforms module (#2291)

* feat: stricter selector parsing, refactor to `platforms` module

- Use a different method to build nothing
- Make the check aware of enable groups

* optimise unit tests - a specific platform module API for all configs

Unit test time: 26.2s -> 13.1s

* Remove unnecessary get_platform_module function

cibuildwheel/platforms/__init__.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from collections.abc import Sequence
+from pathlib import Path
+from typing import Final, Protocol
+
+from cibuildwheel.architecture import Architecture
+from cibuildwheel.options import Options
+from cibuildwheel.platforms import ios, linux, macos, pyodide, windows
+from cibuildwheel.selector import BuildSelector
+from cibuildwheel.typing import GenericPythonConfiguration, PlatformName
+
+
+class PlatformModule(Protocol):
+    # note that as per PEP544, the self argument is ignored when the protocol
+    # is applied to a module
+    def all_python_configurations(self) -> Sequence[GenericPythonConfiguration]: ...
+
+    def get_python_configurations(
+        self, build_selector: BuildSelector, architectures: set[Architecture]
+    ) -> Sequence[GenericPythonConfiguration]: ...
+
+    def build(self, options: Options, tmp_path: Path) -> None: ...
+
+
+ALL_PLATFORM_MODULES: Final[dict[PlatformName, PlatformModule]] = {
+    "linux": linux,
+    "windows": windows,
+    "macos": macos,
+    "pyodide": pyodide,
+    "ios": ios,
+}
+
+
+def get_build_identifiers(
+    platform_module: PlatformModule,
+    build_selector: BuildSelector,
+    architectures: set[Architecture],
+) -> list[str]:
+    python_configurations = platform_module.get_python_configurations(build_selector, architectures)
+    return [config.identifier for config in python_configurations]