Relate user interaction traces back to the initial page load trace

[crdgonzalezca]

• Add initia_load_trace_id to every the user interaction root spans and the initial load root span. This allows the customer to search all traces related to a whole navigation through the initial page.
• Add a link to the initial load trace so the customers can easily go back to the initial trace.

Here is an example on how the user interaction trace looks like:

[codecov-io]

Codecov Report

Merging #145 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #145      +/-   ##
=========================================
+ Coverage   95.88%   95.9%   +0.01%     
=========================================
  Files          30      30              
  Lines         851     855       +4     
  Branches      148     148              
=========================================
+ Hits          816     820       +4     
  Misses         35      35

Impacted Files	Coverage Δ
src/on-page-interaction-stop-watch.ts	100% <0%> (ø)	⬆️
src/initial-load-root-span.ts	100% <0%> (ø)	⬆️

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