New `TypeInfo` struct and `PyStubType` trait #157

Job	Run time
clippy	17s
doc-check	19s
fmt	16s
semver-check	24s
stub-gen (pyo3-stub-gen-testing-pure)	17s
test	21s
stub-gen (pyo3-stub-gen-testing-mixed)	24s
	2m 18s

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