Do not search sys.path for .pxd file if no explicit "cimport" is given

cast PyUnicode_Tailmatch() "Py_ssize_t" result to int rather than propagating its type throughout the code base

Correctly parse dependencies of "cimport foo,bar"

avoid exit overhead in inlined generator expressions by directly returning the result instead of raising a StopIteration with value

re-establish a simple form of generator inlining for any() and all() that does not remove the generator but inlines the evaluation into the inner loop

remove ABC implementations from imports patching code and instead only register Cython's types with the ABCs *iff* they exist
also remove the inspect.iscoroutine() patching as it would only help new code which should use the ABCs in the first place

re-add embed-signatures test for signed char signature (which should not be impacted by the latest implicit signedness change)

I don't know of any platforms where sizeof(long long) == 64, and this
is needed for unsigned long + int64_t on LLP64.

This may pose a problem if sizeof(uintmax_t) > 64.

This makes type promotion rules clearer.

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