lib_performance: centralize systemd-analyze wait logic

Expose wait_analyze_ready() to poll systemd-analyze time safely.
Record systemctl list-jobs whenever boot is not yet finished.
Allow configurable timeout and poll interval via environment variables.
Prepare shared helpers for reuse across performance KPI test suites.

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

Author: smuppand