Allow configuring timeout flag in gitlab-advanced-sast

Proposal

As discussed here, the --timeout flag is not currently exposed by GitLab Advanced SAST.

The purpose of this issue is to allow the --timeout flag to be configured, similar to how this was done in semgrep as part of Allow configuration of semgrep TIMEOUT rule eva... (#345431 - closed) • Adam Cohen, Cody West+ • 17.5.

Implementation Plan

TODO: copy implementation plan from here