NetworkPowerPort: add support for Shelly Gen2+

[aparcar]

Description

The API changed and no longer excepts POST for the legacy API. This commit adds support for the "new" RPC API.

Ref: https://shelly-api-docs.shelly.cloud/gen2/General/RPCProtocol

Tested with a Shelly Plug S MTR Gen3

Checklist

• Documentation for the feature
  • Added in docstring
• Tests for the feature
  • Tested with real hardware

• The arguments and description in doc/configuration.rst have been updated

• Add a section on how to use the feature to doc/usage.rst

• Add a section on how to use the feature to doc/development.rst

• PR has been tested

• Man pages have been regenerated

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 55.7%. Comparing base (6d8febb) to head (ff8223f).
Report is 9 commits behind head on master.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
labgrid/driver/power/shelly_gen2.py	0.0%	12 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1664     +/-   ##
========================================
- Coverage    55.8%   55.7%   -0.1%     
========================================
  Files         170     171      +1     
  Lines       13388   13400     +12     
========================================
  Hits         7472    7472             
- Misses       5916    5928     +12     

Flag	Coverage Δ
3.10	55.7% <0.0%> (-0.1%)	⬇️
3.11	55.7% <0.0%> (-0.1%)	⬇️
3.12	55.7% <0.0%> (-0.1%)	⬇️
3.13	55.7% <0.0%> (-0.1%)	⬇️
3.9	55.7% <0.0%> (-0.1%)	⬇️

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