- operator support NULL constants

[WinkerDu]

Which issue does this PR close?

Closes #1192 .

Rationale for this change

Reproducer:

> select -null;
Internal("(- 'Literal { value: Utf8(NULL) }') can't be evaluated because the expression's type is Utf8, not signed numeric")

The result comes out NULL with this pr

What changes are included in this PR?

• NegativeExpr accepts NULL input then return ScalarValue::Int32(None) as NULL
• do is_signed_numeric type check when NegativeExpr evaluates

Are there any user-facing changes?

[WinkerDu]

@alamb @xudong963 @yjshen plz have a review, thank you.

[liukun4515]

My opinion for this feature or new dialect #1192 (comment)

[WinkerDu]

Close this pr since more conservative opinions of introducing -NULL SQL dialect, see #1192