allow stdlib+compiler to have their own locked down, isolated nimble dependencies that live in a separate namespace (eg stdx/regex)

[timotheecour]

the following would IMO be the perfect solution, allowing stdlib/compiler/tools to use nimble packages, while not clashing with user installed packages

import std/strutils # stdlib
import stdx/regex # controlled via `nimble install regex` from compiler installation, using fixed hashes for all dependent pkgs
import pkg/regex # controlled via `nimble install regex` from user; stdx/regex and pkg/regex resolve as separate modules
import regex # same as pkg/regex

the rare case of exportc procs can be dealt with using a exportc prefix (eg "stdx") to avoid duplicate definition errors

the stdx prefix is not even essential, ie, std/regex could be used to, and modules could transparently be re-mapped to a separate nimble package without breaking user code nor interfering with user installed nimble packages (which could be a different version or same, irrelevant) ; neat.

links

• Nimble improvements nim-lang/RFCs#398
• https://gist.github.com/genotrance/ee2ce321a56c95df2d4bb7ce4bd6b5ab
• added Atlas helper tool nim-lang/Nim#18497
• https://research.swtch.com/version-sat