fix(tianmu): fix crash when the aggregated element was decimal (#1402)

[adofsauron]

1. Fix the crash first
2. then redesign the entire aggregated data stream

Summary about this PR

Issue Number: close #1402

Tests Check List

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Changelog

• New Feature
• Bug Fix
• Performance Improvement
• Build/Testing/CI/CD
• Documentation
• Not for changelog (changelog entry is not required)

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features

[mergify]

This pull request's title should follow requirements next. @adofsauron please check it 👇.

Valid format:

fix(vc): fix sth..... (#3306)
  ^         ^---------^  ^----^
  |         |            |
  |         +            +-> you issue id.
  |         |
  |         +-> Summary in present tense.
  |
  +-------> Type: feat, fix, docs, workflow, style, refactor, test, website, chore

Valid types:

• feat: new feature for stonedb
• fix: bug fix for stonedb
• docs: changes to the documentation
• workflow: ci/cd in .github
• perf: Changes to improve code performance
• refactor: refactoring production code, eg. renaming a variable
• style: formatting, missing semi colons, etc; no production code change
• test: adding missing tests, refactoring tests; no production code change
• website
• chore: updating grunt tasks etc; no production code change

[mergify]

Thanks for the contribution!
I have applied any labels matching special text in your PR Changelog.

Please review the labels and make any necessary changes.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.05 ⚠️

Comparison is base (9c87c73) 44.91% compared to head (838a5d1) 44.86%.

❗ Current head 838a5d1 differs from pull request most recent head f57ee36. Consider uploading reports for the commit f57ee36 to get more accurate results

Additional details and impacted files

@@                 Coverage Diff                 @@
##           stonedb-5.7-dev    #1506      +/-   ##
===================================================
- Coverage            44.91%   44.86%   -0.05%     
===================================================
  Files                 1999     1999              
  Lines               413910   413913       +3     
===================================================
- Hits                185902   185712     -190     
- Misses              228008   228201     +193     

Impacted Files	Coverage Δ
sql/item.h	41.75% <ø> (-0.13%)	⬇️
storage/tianmu/core/item_tianmu_field.h	67.56% <ø> (ø)
storage/tianmu/core/pack_guardian.cpp	42.75% <ø> (ø)
storage/tianmu/core/aggregation_algorithm.cpp	56.27% <100.00%> (-0.09%)	⬇️
storage/tianmu/core/item_tianmu_field.cpp	91.53% <100.00%> (+0.18%)	⬆️

... and 92 files with indirect coverage changes

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[konghaiya]

LGTM