Add ssObject designation search across LSST and ZTF

[thomasculino]

This PR is built on boom-astro#497 and requires it to be merged before this one. In this one we aim to prepare the search on the frontend by ssObjectId. To do so, we:

• Adds a designation search mode to GET /babamul/objects, looking up a Solar System object by MPC designation independently across LSST (designation field) and ZTF (ssnamenr) — an object may exist in only one survey, both, or neither, and results from each are returned as-is rather than merged.
• Gates the ZTF side on ssdistnr <= ZTF_POSITION_UNCERTAINTY (via $elemMatch) since ssnamenr is only ZTF's nearest known SSO within ~30″, not a confirmed identification — without this, a detection merely near a catalogued asteroid's track would falsely show up as a match.
• Adds a compound (ssnamenr, ssdistnr) index on ZTF_alerts_aux to support the lookup.
  Depends on # (lsst-ssobject-ingestion), which adds the designation field this builds on — base branch for this PR should be set to lsst-ssobject-ingestion, not main.

For ZTF, whether this method is the method we should use in the end is still uncertain. I'm open to suggestions.

[github-actions]

Throughput results (56a79f1b5a22aba36555f522ddb8c4427498f9c3):

Storage	New wall time	Baseline wall time	Difference
mongo	257.0	250.9	2.00%
s3	268.1	173.5	54.00%

Baseline run: 28049059808