remote/client: support OpenOCD bootstrap without environment

[ozan956]

The bootstrap fallback path was too narrow for OpenOCD-based setups without a
local environment.

Previously, labgrid-client bootstrap only auto-created OpenOCDDriver for
NetworkAlteraUSBBlaster. If a place exposed only NetworkUSBDebugger, the
client still failed with target has no compatible resource available even
though OpenOCDDriver can bind to that resource type.

The existing bootstrap_args path was also too limited. It only handled raw
key=value strings, which was not sufficient for OpenOCDDriver arguments
such as load_commands, search, or config, where structured values like
lists are often required.

This change:

• extends the bootstrap fallback to NetworkUSBDebugger
• parses bootstrap driver arguments as YAML values
• allows structured OpenOCD driver arguments to be passed directly from the CLI

This makes CLI-only OpenOCD bootstrap flows usable in more cases without
requiring a local environment file.

I verified the change with focused regression tests:

pytest -q tests/test_client.py -k 'bootstrap_network_usb_debugger or bootstrap_openocd_args'

Checklist

• Tests for the feature
• PR has been tested

[codecov]

Codecov Report

❌ Patch coverage is 13.33333% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.7%. Comparing base (ec5ec29) to head (91725b3).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
labgrid/remote/client.py	13.3%	13 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1864     +/-   ##
========================================
- Coverage    45.8%   45.7%   -0.1%     
========================================
  Files         182     182             
  Lines       14720   14733     +13     
========================================
+ Hits         6743    6745      +2     
- Misses       7977    7988     +11     

Flag	Coverage Δ
3.10	45.7% <13.3%> (-0.1%)	⬇️
3.11	45.7% <13.3%> (-0.1%)	⬇️
3.12	45.7% <13.3%> (-0.1%)	⬇️
3.13	45.7% <13.3%> (-0.1%)	⬇️
3.14	45.7% <13.3%> (-0.1%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.