Rewrite send-to-lava.sh from scratch and drop legacy Linaro version

- Reimplemented the LAVA signal emitter script to be POSIX-compliant, shellcheck-clean, and dmesg-safe.
- Removed FIFO-based signaling and replaced it with a buffered atomic flush approach.
- Handles only valid PASS/FAIL/SKIP/UNKNOWN results with robust parsing.
- Dropped the legacy script sourced from Linaro test definitions and removed the old license file.
- This version ensures clean output, avoids malformed signals, and is CI-friendly.

Signed-off-by: Srikanth Muppandam <[email protected]>

Author: smuppand