Store Decimal precision and size while normalising

[GuptaManan100]

Description

This PR fixes part of the issue described in #15784.

As described in #15784 (comment), the problem arises because when Vtgates normalize the decimal values, they don't store the scale and length. This PR makes this change by adding 2 more fields to the Arguments struct.

This also affects the caching of queries. Since the precision of 100.01 and 100.0001 are different, queries that only differ in this literal will actually have different results and shouldn't be cached to the same plan.

In order to find the size and precision of the decimal value, we are relying on the existing code in decimal package to parse the decimal value and return the exponent and the size.

https://dev.mysql.com/doc/refman/8.3/en/precision-math-decimal-characteristics.html page talks about decimal value and its handling of length and precision

Related Issue(s)

• Fixes Bug Report: TPCH query returns incorrect precision count in the fields #15784. With Fix Scale and length handling in CASE and JOIN bind variables #15787 being merged, this PR resolves the remaining issue in Bug Report: TPCH query returns incorrect precision count in the fields #15784.

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[vmg]

I think adding the size/scale to the bind var replacement is a good idea. Let's simplify the calculation of the values though.

[vmg]

Looking bueno. Thanks manan!

[GuptaManan100]

Awesome!!! Thank you everyone for the reviews! The last commit adds the complete Q14 to the test suite verifying that the query works now!

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 68.43%. Comparing base (96b1419) to head (0588f63).
Report is 2 commits behind head on main.

Files	Patch %	Lines
go/vt/sqlparser/normalizer.go	60.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15785      +/-   ##
==========================================
- Coverage   68.44%   68.43%   -0.01%     
==========================================
  Files        1558     1558              
  Lines      195822   195928     +106     
==========================================
+ Hits       134032   134087      +55     
- Misses      61790    61841      +51     

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