fix(spans): Add missing functions for db view

[wmak]

• Adds time_spent_percentage to the spans dataset
• Adds http_response_count
• Adds count_web_vitals

[codecov]

Codecov Report

Attention: Patch coverage is 58.62069% with 12 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/search/events/datasets/spans_indexed.py	58.62%	9 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #78224      +/-   ##
==========================================
- Coverage   78.10%   78.10%   -0.01%     
==========================================
  Files        7038     7038              
  Lines      311549   311573      +24     
  Branches    50924    50930       +6     
==========================================
+ Hits       243347   243355       +8     
- Misses      56450    56466      +16     
  Partials    11752    11752              

[0Calories]

LGTM

[getsantry]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you remove the label Waiting for: Community, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀