lib_display: add helper to best-effort force primary output to 1080p60@60

Avoid restarting Weston when it is not running (improves first-run stability)
Restart Weston only when needed to apply weston.ini updates
Harden weston process detection and silence ShellCheck SC2009 where required
Keep changes non-fatal: mode enforcement remains best-effort for CI

Signed-off-by: Srikanth Muppandam <smuppand@qti.qualcomm.com>

Author: smuppand