Fix TPCH test by providing the correct field information in evalengine

[GuptaManan100]

Description

This PR fixes the issue described in #15643

While investigating the issue, it was found that we weren't copying the column length and the scale from the fields information we got back from MySQL. This caused evalengine to mess up the calculation of the final scale in the output columns.

This PR adds the tests to our infrastructure. It also adds a unit test and then fixes the bug.

Related Issue(s)

• Fixes Bug Report: TPCH query fields incorrect in sharded environment #15643

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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[codecov]

Codecov Report

Attention: Patch coverage is 91.48936% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 68.12%. Comparing base (28988ff) to head (09eab1c).
Report is 4 commits behind head on main.

Files	Patch %	Lines
go/vt/vtgate/evalengine/compiler.go	50.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15623   +/-   ##
=======================================
  Coverage   68.12%   68.12%           
=======================================
  Files        1556     1556           
  Lines      194984   195019   +35     
=======================================
+ Hits       132840   132865   +25     
- Misses      62144    62154   +10     

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