editoast: add tracing for ping operations

[woshilapin]

It seems that our healtcheck needs a relatively long time (#10026) but we're missing information about what could take time. Let's first add a way to measure it and see what we can do with it later.

[flomonster]

LGTM

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.83%. Comparing base (4e1462b) to head (a49627f).
Report is 4 commits behind head on dev.

Files with missing lines	Patch %	Lines
editoast/src/core/mq_client.rs	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #10129   +/-   ##
=======================================
  Coverage   79.83%   79.83%           
=======================================
  Files        1054     1054           
  Lines      105536   105520   -16     
  Branches      726      726           
=======================================
- Hits        84250    84238   -12     
+ Misses      21244    21240    -4     
  Partials       42       42           

Flag	Coverage Δ
editoast	73.74% <66.66%> (-0.01%)	⬇️
front	89.14% <ø> (ø)
gateway	2.18% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.50% <ø> (ø)
tests	87.00% <ø> (ø)

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