ref(metrics-layer): Test the span metric charts too

[wmak]

• This adds the metrics-layer feature flag to the span metrics event-stats tests too

[codecov]

Codecov Report

Merging #54045 (910e4ae) into master (e658f63) will increase coverage by 0.00%.
Report is 31 commits behind head on master.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #54045   +/-   ##
=======================================
  Coverage   79.53%   79.54%           
=======================================
  Files        4974     4974           
  Lines      210394   210386    -8     
  Branches    35836    35832    -4     
=======================================
+ Hits       167339   167347    +8     
+ Misses      37907    37895   -12     
+ Partials     5148     5144    -4     

Files Changed	Coverage Δ
...tatic/app/views/replays/replayTable/headerCell.tsx	66.66% <ø> (ø)
static/app/views/replays/replayTable/index.tsx	88.23% <ø> (ø)
static/app/views/replays/replayTable/tableCell.tsx	88.88% <ø> (ø)

... and 31 files with indirect coverage changes