feat(expr): support sign and distinguish is_positive vs is_sign_positive

[xiangjinwu]

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What's changed and what's your intention?

Support PostgreSQL expression sign for decimal and double precision (Resolves #8900). Input numeral of other types would be implicitly casted to double precision as in PostgreSQL.

It does not map to rust signum directly:

value	sign	signum	is_positive	is_negative	is_sign_positive	is_sign_negative	num_traits is_positive	num_traits is_negative
-0.0	0	-1	x	x	false	true	false	true
0.0	0	1	x	x	true	false	true	false
0	0	0	false	false	x	x	false	false

Given that num_traits::Signed confuses between is_positive and is_sign_positive. We removed its usage.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR contains user-facing changes.

Types of user-facing changes

• SQL commands, functions, and operators

Release note

Support PostgreSQL expression sign for decimal and double precision.

[codecov]

Codecov Report

Merging #10819 (90bfe60) into main (b70987e) will increase coverage by 0.00%.
The diff coverage is 27.58%.

@@           Coverage Diff           @@
##             main   #10819   +/-   ##
=======================================
  Coverage   70.07%   70.08%           
=======================================
  Files        1300     1300           
  Lines      222084   222034   -50     
=======================================
- Hits       155628   155615   -13     
+ Misses      66456    66419   -37     

Flag	Coverage Δ
rust	70.08% <27.58%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/common/src/types/decimal.rs	66.43% <0.00%> (+2.60%)	⬆️
src/common/src/types/interval.rs	81.18% <ø> (-0.06%)	⬇️
src/common/src/types/num256.rs	72.78% <ø> (+2.44%)	⬆️
src/expr/src/vector_op/round.rs	92.50% <ø> (ø)
src/frontend/src/expr/pure.rs	93.44% <ø> (ø)
src/expr/src/vector_op/arithmetic_op.rs	65.67% <27.77%> (-1.59%)	⬇️
src/common/src/types/ops.rs	100.00% <100.00%> (ø)
src/common/src/types/ordered_float.rs	51.30% <100.00%> (+0.91%)	⬆️
src/frontend/src/binder/expr/function.rs	85.23% <100.00%> (+0.01%)	⬆️

... and 1 file with indirect coverage changes

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[BugenZhao]

LGTM!