fix(udf): avoid panic on invalid output and fix decimal output scale lost

[wangrunji0408]

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What's changed and what's your intention?

This PR fixed the panic:

failed to convert UDF output to DataChunk: FromArrow("invalid decimal: \"-5.10043e-05\"")

First of all, as mentioned in #9002, compute nodes must not panic on errors caused by UDF servers. cc @KveinAxel

Next, after #11839, decimal values are stored as strings in the arrow array. However, the panic message indicates that a float number with scientific notation -5.10043e-05 was written by Python, and it couldn't be parsed by rust decimal. It turned out that user defined a function returning NUMERIC, but the actual return value is a float rather than Decimal. Even it returns a Decimal, its string form may still contains scientific notation and has a long precision number.

>>> from decimal import Decimal
>>> str(Decimal(1e-10))
'1.0000000000000000364321973154977415791655470655996396089904010295867919921875E-10'

When parsed by RisingWave, the tailing numbers and exponent will be truncated, resulting in wrong results.

dev=> select decimal();
            decimal             
--------------------------------
 1.0000000000000000364321973155

So, this PR:

1. check the return value for Python functions that return DECIMAL and reject values other than Decimal type. (this problem doesn't exist in Java because it's strong typed)
2. format printing decimals in Python and Java to avoid scientific notation

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• 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 needs documentation updates. (Please use the Release note section below to summarize the impact on users)

[xxchan]

What happens if we only change this line without changing udf sdk? 🤔

[wangrunji0408]

will result in expression error: invalid decimal, or silently produce wrong value 1e-10 -> 1.000...

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (59d56c3) 68.24% compared to head (7000acb) 68.23%.
Report is 8 commits behind head on main.

Files	Patch %	Lines
src/expr/core/src/expr/expr_udf.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13828      +/-   ##
==========================================
- Coverage   68.24%   68.23%   -0.01%     
==========================================
  Files        1525     1525              
  Lines      262214   262212       -2     
==========================================
- Hits       178946   178920      -26     
- Misses      83268    83292      +24     

Flag	Coverage Δ
rust	68.23% <0.00%> (-0.01%)	⬇️

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[yufansong]

LGTM