feat: struct util fns

[anthonyjoeseph]

Closes #1460

Credit to @samhh for omit and pick , @gcanti and @qlonik for everything else.

Note: I was unable to get the function overloading quite right for mapAtE - the existing solution works afaik but it's a bit bloated & ugly

[anthonyjoeseph]

Converting to draft until the following are fixed:

• omit & pick have autocomplete ✅
• renameAt uses EnsureLiteral ✅

I'll also continue to work on the mapAtE function signature

[anthonyjoeseph]

I've realized that EnsureLiteral is at odds with autocomplete because autocomplete depends on a union of possibilities. So I've used EnsureLiteral for non-piped contexts only. It's a compromise to be sure, but I think it's a good balance of usability & safety

Here's a little example showing the pros/cons of this

[anthonyjoeseph]

Closing in favor of spectacles-ts