sim._pyrtl: py3.12+: convert to int before bitwise negating.

Amaranth bitwise negation `~` compiles to Python bitwise negation `~` in
simulation; the same holds for comparison operators such as `==`. Thus
an expression such as `~(a == b)` in simulation will compile to Python
that takes the bitwise negation of the comparison result, which will be
an actual bool.

On 3.12, the result is a `DeprecationWarning` emitted only at simulation
run-time.

When negating in simulation, coerce the value to an int. `mask` is
sufficient as we do no further arithmetic here.

amaranth/sim/_pyrtl.py

@@ -138,7 +138,7 @@ class _RHSValueCompiler(_ValueCompiler):
         if len(value.operands) == 1:
             arg, = value.operands
             if value.operator == "~":
-                return f"(~{self(arg)})"
+                return f"(~{mask(arg)})"
             if value.operator == "-":
                 return f"(-{sign(arg)})"
             if value.operator == "b":