feat(agent): send phase status code upon phase completion

[rene-oromtz]

Description

This is a follow-up on the logging redesign, since logs are now NOT transmitted at the end of the job execution, we can also send the phase status upon phase completion.

1. This PR removes storing output and serial output in the testflinger-outcome.json, in the logging redesign, they were removed anyway while submitting results (pop'ed). While not important as of now, but this reduces the size of this file as its not storing any log output at all.
2. Send status updates (exit code) once the phase is completed. With this server keeps track of each phase completion immediately showing the results for that phase even when the job is not completed.
3. Other minor modification includes replacing some uses of os.path to Path instead.

This is also a step forward to be able to show live output in the UI

Resolved issues

Resolves CERTTF-770

Documentation

Web service API changes

Tests

All current unit tests were passing, some needed minor modifications related to the usage of Pathlib.
Phase related tests were modified to match this new behavior and added couple more.

Tested as well on staging.

Job at test phase. Provision logs are already available in the UI

Job at reserve phase. Provision and test logs are already available in the UI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.99%. Comparing base (38ec676) to head (5c11170).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #846      +/-   ##
==========================================
- Coverage   71.01%   70.99%   -0.02%     
==========================================
  Files         108      108              
  Lines        9583     9578       -5     
  Branches      854      852       -2     
==========================================
- Hits         6805     6800       -5     
  Misses       2608     2608              
  Partials      170      170              

Flag	Coverage Δ		*Carryforward flag
agent	72.85% <100.00%> (-0.12%)	⬇️
cli	87.78% <ø> (ø)		Carriedforward from b928f1e
device	54.22% <ø> (ø)		Carriedforward from b928f1e
server	87.71% <ø> (ø)		Carriedforward from b928f1e

*This pull request uses carry forward flags. Click here to find out more.

Components	Coverage Δ
Agent	72.85% <100.00%> (-0.12%)	⬇️
CLI	87.78% <ø> (ø)
Common	∅ <ø> (∅)
Device Connectors	54.22% <ø> (ø)
Server	87.71% <ø> (ø)

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[ajzobro]

Makes sense.