Add pass to fold type transformations into function signature

[anwang2009]

As title.

This transformer gives users more control over where preprocessing steps may be located, and what input types their relay program can accept

[jroesch]

cc @electriclilies can you review this one?

[electriclilies]

Some general comments -- overall looks like you are on the right track!
(Also I realized after reviewing that this is still marked as draft, oops. let me know when it is ready for another review and I'll take a look again)

[electriclilies]

After taking another look, I'm a bit confused how you're doing the rewrite of the function parameters, added some questions related to that

[electriclilies]

Overall, LGTM, would be great if you could add one comment to the CallNode visitor saying that that logic is only for removing the casts, and also change the opt level

[masahi]

@anwang2009 Please take a look at the CI problem.

[AndrewZhaoLuo]

@anwang2009 do you still have interest in merging this PR?

[areusch]

@AndrewZhaoLuo@anwang2009 are you guys doing this as part of #8296 or is that just related?

[AndrewZhaoLuo]

@anwang2009 any plans to continue working on this PR?

I think people do request things like this.

[anwang2009]

Unrelated to that issue linked. I plan to continue working on this, I just need to find the time 🙃
Sorry for the languishing, I'll try to get something in by start of next week.