[WIP] Add a non-noPos call position to primops

[roberth]

Motivation

Pass a Pos to primops, so that warn can print a position.

Notably, the position works well with partial application, such as here:

let
  warnIf = c: s: if c then builtins.warn s else null;
in
  builtins.warn "hI"
  (warnIf true "ok" 1213)

Both warning calls print their most relevant position.

TODO:

• The simple change of forwarding pos caused a number of duplicate positions to be printed. The deduplication isn't quite done.

Context

• Is relevant to, and currently includes commits from Add builtins.warn #10592

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