ci: Add hardware-in-the-loop testing workflow

Add GitHub Actions workflow for automated hardware testing on AST1060.
The workflow runs in two stages:

1. Precommit checks on ubuntu-22.04:
   - Verify Cargo.lock
   - Run cargo xtask precommit (format/lint/build)
   - Upload bloat reports

2. Hardware functional tests on self-hosted runner with AST1060:
   - Build firmware with test features (hmac, hash, rsa, ecdsa)
   - Generate UART boot image with proper 4-byte size header
   - Upload firmware via UART following AST1060 boot protocol
   - Monitor test execution and parse PASS/FAIL/SKIP results
   - Upload test logs and artifacts

The workflow supports manual triggering with test suite selection and
only runs hardware tests if precommit checks pass.

Author: rusty1968