wire fbuild LpcDeployer to prefer probe-rs when CMSIS-DAP probe enumerates (#930 follow-up)

[zackees]

Split-out of #930 (now closed).

Scope

Once the patched probe-rs binaries are hosted (sibling cross-compile issue), plumb them into fbuild's LPC deploy path:

• Extend fbuild_deploy::lpc_debugger_reflash (or a sibling probe_rs module) with find_probe_rs() and install_probe_rs() mirroring the existing find_dfu_util / find_lpc21isp shape.
• Update LpcDeployer::deploy to check serialport::available_ports() for a CMSIS-DAP probe on the requested port. If found AND probe-rs is available, prefer the probe-rs SWD path over lpc21isp UART ISP.
• Retain lpc21isp as the fallback for boards without a CMSIS-DAP debugger (or where probe-rs itself fails for platform reasons).
• Add a fbuild deploy … --no-probe-rs opt-out for users who want to force the lpc21isp path.

Acceptance

• fbuild deploy tests/platform/lpc845brk -e lpc845brk --port COM10 completes without any button press against the factory LPC-Link2 v1.0.7 firmware.
• fbuild deploy … --no-probe-rs still routes through lpc21isp (regression guard).
• End-to-end unit tests cover the dispatch logic.

Related

• probe-rs on LPC-Link2 CMSIS-DAP v1.0.7: series of upstream quirks to patch through #930 (parent umbrella, closed)
• fbuild deploy: own nxplpc/LPC8xx flash end-to-end (FastLED is removing its direct pyocd path) #921 (parent tracking issue for LPC845-BRK end-to-end deploy)