chore(dist): add option to dump and restore scan config for distributed scans (semgrep/semgrep-proprietary#5924)

Lockfileless-preresolve scans, which look similar to distributed scans,
currently fetch the config once for the first half of the scan and again
for the
last half of the scan. This is inefficient because fetching the scan
config is
very slow. This PR exposes a way to dump the scan config and resume
later from
a dumped scan config. This is an experimental flag that should only be
used in SMS.

synced from Pro 972cd3b28d2b3dc37cb28bb8e5d9ade3f8a74201