Export flamegraph and table to pdf/png

[cjsampson]

This PR adds the ability to export the flamegraph as a PNG/PDF and the table pane as a PDF.

[codecov]

Codecov Report

Merging #143 (e8a66e5) into main (d173be8) will increase coverage by 2.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #143      +/-   ##
==========================================
+ Coverage   55.35%   57.50%   +2.16%     
==========================================
  Files          69       69              
  Lines        2631     2630       -1     
==========================================
+ Hits         1456     1512      +56     
+ Misses       1071      998      -73     
- Partials      104      120      +16     

Impacted Files	Coverage Δ
pkg/agent/session.go	68.61% <0.00%> (-4.65%)	⬇️
pkg/storage/segment/segment.go	92.50% <0.00%> (-4.16%)	⬇️
pkg/server/controller.go	25.75% <0.00%> (+25.75%)	⬆️
pkg/server/ingest.go	66.04% <0.00%> (+66.04%)	⬆️
pkg/server/stats.go	66.67% <0.00%> (+66.67%)	⬆️

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[Rperry2174]

Thanks @cjsampson just a couple of small changes we appreciate you adding this for us!