refactor(users/sterni/nix): move generic number operation into num

We omit type checks for performance reasons in most places currently, so
the library grouping is important in showing people what to use for what
sort of input. The moved functions make sense to use with floats as
well, so we'll move them to the num library. Some of the remaining
functions could theoretically be adapted and moved, but aren't for now.

Change-Id: Ifdecaa60be594f4438b2a58b9ea6445e2da080e3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9007
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

users/sterni/nix/int/tests/default.nix

@@ -15,9 +15,6 @@ let
     ;
 
   testBounds = it "checks minBound and maxBound" [
-    # this is gonna blow up in my face because
-    # integer overflow is undefined behavior in
-    # C++, so most likely anything could happen?
     (assertEq "maxBound is the maxBound" true
       (int.maxBound + 1 < int.maxBound))
     (assertEq "minBound is the minBound" true
@@ -321,7 +318,6 @@ let
   testBasic = it "checks basic int operations" [
     (assertEq "122 is even" (int.even 122 && !(int.odd 122)) true)
     (assertEq "123 is odd" (int.odd 123 && !(int.even 123)) true)
-    (assertEq "abs -4959" (int.abs (-4959)) 4959)
   ];
 
   expNumbers = [
@@ -374,7 +370,7 @@ let
   checkShiftLMulExp = n:
     assertEq "${toString n} >> 6 == ${toString n} * 2 ^ 6"
       (int.bitShiftL n 5)
-      (int.mul n (int.exp 2 5));
+      (n * (int.exp 2 5));
 
   testBit = it "checks bitwise operations" (lib.flatten [
     (builtins.map checkShift shifts)