Allow customizing GriffeLoader.allow_inspection

[BlueGlassBlock]

When utilizing native extensions, griffe will first use inspect to load native extension as a base, however that may produce confusing result by "leaking" APIs from native level, or produce confusing tag on methods/properties. So I think allowing toggling inspection is useful to make griffe only analyze modules statically.

For reference, see my testing repo: https://github.com/BlueGlassBlock/mkdocstrings-native-test

[pawamoy]

Thanks, good use-case for Griffe's allow_inspection option 👍 Thanks for the PR!