Show generalized cost in debug UI

[leonardehrenfried]

Summary

This adds the generalized cost for legs and itineraries to the debug UI. It looks like this:

In order to make some room, I formatted the leg duration a bit more compactly.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.85%. Comparing base (31c40f7) to head (edcba5a).
Report is 35 commits behind head on dev-2.x.

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #6336   +/-   ##
==========================================
  Coverage      69.84%   69.85%           
- Complexity     17907    17921   +14     
==========================================
  Files           2034     2035    +1     
  Lines          76444    76495   +51     
  Branches        7820     7824    +4     
==========================================
+ Hits           53396    53434   +38     
- Misses         20315    20324    +9     
- Partials        2733     2737    +4     

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[miklcct]

I think that the use of a dollar sign may be a bit misleading, as the generalized cost is measured in terms of time, not in terms of money. This is particularly relevant if we are going to show the fare information in the debug UI as well.

[testower]

Code looks good to me