Add mode for initializing from gstLAL info

We currently have two alternatives to choose from: init_range and overlap_bank. We need a third alternative, which makes us use gstLAL's search results.

There are different ways we could do this, but the following is proposed:

1. Per-event information should be stored in GraceDB, so we do not need to provide that as it's derivable from the event name
2. SVD bank bin edges should be fixed over an observing run, and are kept in a single file. This file is relatively static -- it might change between O4a and O4b, or if some overall change to gstLAL is needed for an unforeseen reason, but it should be constant over a span of \mathcal{O}(\text{months}). So while we could hard-code this into the pipeline, it makes more sense to make it a config option, and hard-code the path in GWCelery's config file template.

So we just need to add this third config parser mode, and add a third branch to the existing two in cli.py to read from graceDB and parse the file.