fix(specifiers): === uses original string, not normalized, when available

[notatallshaw]

Fixes #978
Fixes #766

[notatallshaw]

Setuptools test fails because in the test suite it passes ['>=3.0', '!=3.1'] into SpecifierSet this is against the type hint str | Iterable[Specifier].

I can handle this for now, but I think raising a PR on setuptools side makes sense also.

[henryiii]

So internally this could be storing strings or Specifiers? With SpecifierSet("...") being different from SpecifierSet(["..."])? Seems like we should always make this hold specifiers?

[notatallshaw]

So internally this could be storing strings or Specifiers? With SpecifierSet("...") being different from SpecifierSet(["..."])? Seems like we should always make this hold specifiers?

We could at a isinstance check and expand the type to str | Iterable[Specifier | str] or deprecation warning followed eventually by an assert?

I really don't know what the move is when the type hint is quite clear but the downstream decides to pass something else in, let it be, make it fail, support the use case?

[notatallshaw]

We could at a isinstance check and expand the type to str | Iterable[Specifier | str] or deprecation warning followed eventually by an assert?

Well, either way, this PR doesn't affect this, it just don't break users who do pass in a Iterable[str] in the constructor. We can make a separate issue for this.