Cross-crate self as argument method calls

[nrc]

r?

closes #18061

[nrc]

r? @nikomatsakis

[alexcrichton]

also cc @pcwalton, you may be able to review this (we've gotten a lot of duplicate reports about this).

@nick29581, looks like this needs a rebase as well.

[nikomatsakis]

r+ if foo is renamed to something else -- I think there's further cleanup to be done by unifying method/static-method treatment but not necessarily as part of this PR.

[japaric]

@nick29581 This needs a rebase