Implementation of port discovery through Pluggable discovery

[cmaglie]

trafficstars

Please check if the PR fulfills these requirements

• [X] The PR has no duplicates (please search among the Pull Requests before creating one)
• [X] Tests for the changes have been added (for bug fixes / features)

• What kind of change does this PR introduce? The port discovery is offloaded from the agent and it's made available through pluggable-discoveries (as done other Arduino software products like Arduino IDE or Arduino CLI)

• What is the current behavior? The port discovery subroutine was embedded in the Create Agent (leading to code duplication and double maintenance effort)

• What is the new behavior? The port discovery subroutine is off-loaded to pluggable discvoeries.

• Does this PR introduce a breaking change? No

• Other information: Supersedes #773

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 1.53846% with 128 lines in your changes are missing coverage. Please review.

Project coverage is 20.90%. Comparing base (ef266fa) to head (36bdf7b).

Files	Patch %	Lines
serial.go	0.00%	113 Missing :warning:
main.go	0.00%	9 Missing :warning:
serialport.go	0.00%	4 Missing :warning:
conn.go	0.00%	1 Missing :warning:
hub.go	0.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #900      +/-   ##
==========================================
+ Coverage   20.89%   20.90%   +0.01%     
==========================================
  Files          43       42       -1     
  Lines        3164     3157       -7     
==========================================
- Hits          661      660       -1     
+ Misses       2406     2400       -6     
  Partials       97       97              

Flag	Coverage Δ
unit	20.90% <1.53%> (+0.01%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.