fix: Stacked charts with numerical columns

[michael-s-molina]

SUMMARY

#26087 added support for numerical x-axis but ended up introducing #26255 and #26256 because ECharts does not support stacked charts with numerical x-axis. This PR converts the x-axis to type category when a chart is stacked.

Fixes: #26255
Fixes: #26256

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

1 - Create a stacked chart with a numerical x-axis
2 - Make sure the axis and tooltip are calculated correctly

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

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 69.18%. Comparing base (578a899) to head (3c80862).
Report is 2263 commits behind head on master.

Files with missing lines	Patch %	Lines
...hart-echarts/src/MixedTimeseries/transformProps.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #26264      +/-   ##
==========================================
- Coverage   69.18%   69.18%   -0.01%     
==========================================
  Files        1945     1945              
  Lines       75948    75948              
  Branches     8460     8460              
==========================================
- Hits        52545    52542       -3     
- Misses      21218    21221       +3     
  Partials     2185     2185              

Flag	Coverage Δ
javascript	56.50% <66.66%> (-0.01%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[sfirke]

I can't speak with authority to the code so would like @villebro to review as well - but the fix looks good to me on the surface!

[justinpark]

LGTM

[villebro]

LGTM to unblock. Let's collab on adding upstream support for this to ECharts.