fix: stop treating arithmetic negation as bitwise NOT

[Amogh-2404]

Which issue does this PR close?

• Closes Expression simplifier treats arithmetic negation as bitwise NOT #24665.

Rationale for this change

Expr::Negative represents unary minus, but the simplifier applied identities for bitwise NOT. This produced wrong results in bitwise expressions and could hide signed-integer overflow when removing double negation.

What changes are included in this PR?

• Remove the bitwise-complement and De Morgan rewrites for Expr::Negative.
• Remove the helpers used only by those rewrites.
• Replace the invalid unit expectations with preservation tests and add an end-to-end regression in scalar.slt.

Are these changes tested?

Yes. Unit tests cover both operand orders for AND, OR, and XOR, the two De Morgan shapes, and double negation. scalar.slt checks the resulting values end to end.

Are there any user-facing changes?

Yes. Unary minus in bitwise expressions now returns the correct results, and double negation preserves overflow behaviour. There are no API changes.

[Amogh-2404]

Continued in #24668 after renaming the branch.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.43%. Comparing base (63f5b55) to head (c37e666).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24666      +/-   ##
==========================================
- Coverage   81.44%   81.43%   -0.01%     
==========================================
  Files        1118     1118              
  Lines      399550   399478      -72     
  Branches   399550   399478      -72     
==========================================
- Hits       325398   325333      -65     
+ Misses      55154    55152       -2     
+ Partials    18998    18993       -5     

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