fix(legacy-chart): corrupted raw chart data

[justinpark]

SUMMARY

In legacy charts, there's some logics mutating chartData which also corrupts the original raw data.
This makes the invalid chart results specially in the stacked chart which sums up the series values for the chart data.
This commit makes the copy of the rawData value to avoid the corruption.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

After:

after--polluted-rawData.mov

Before:

before--polluted-rawData.mov

TESTING INSTRUCTIONS

• Create a area chart
• set stacked
• choose a Y A-axis format like .3s

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #24850 (2aadb08) into master (e2d5046) will increase coverage by 0.00%.
Report is 6 commits behind head on master.
The diff coverage is 95.69%.

❗ Current head 2aadb08 differs from pull request most recent head 4d20cb6. Consider uploading reports for the commit 4d20cb6 to get more accurate results

@@           Coverage Diff           @@
##           master   #24850   +/-   ##
=======================================
  Coverage   68.99%   69.00%           
=======================================
  Files        1903     1904    +1     
  Lines       74072    74106   +34     
  Branches     8193     8193           
=======================================
+ Hits        51107    51137   +30     
- Misses      20844    20848    +4     
  Partials     2121     2121           

Flag	Coverage Δ
javascript	55.83% <0.00%> (-0.01%)	⬇️

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

Files Changed	Coverage Δ
...ins/legacy-preset-chart-nvd3/src/transformProps.js	7.14% <0.00%> (-0.27%)	⬇️
superset/advanced_data_type/api.py	100.00% <ø> (ø)
superset/annotation_layers/annotations/api.py	89.23% <ø> (ø)
superset/annotation_layers/annotations/schemas.py	100.00% <ø> (ø)
superset/annotation_layers/api.py	86.20% <ø> (ø)
superset/annotation_layers/schemas.py	100.00% <ø> (ø)
superset/async_events/api.py	100.00% <ø> (ø)
superset/available_domains/api.py	100.00% <ø> (ø)
superset/cachekeys/api.py	96.15% <ø> (ø)
superset/charts/api.py	87.82% <ø> (ø)
... and 57 more

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[michael-s-molina]

LGTM