Bug in `gc.rs` causing a `sqlx` panic that completely crashes `atticd`

[ixmatus]

Specifically, we're getting this panic from atticd:

thread 'main' panicked at 'assertion failed: self.param_types.len() <= (u16::MAX as usize)'

... which is related to this sqlx issue: launchbadge/sqlx#671 (comment) but only because the number of chunks to garbage collect have grown beyond psql's purported bind parameter limit.

We narrowed the issue down (via the stack trace) to this query:

attic/server/src/gc.rs

Line 184 in 6eabc3f

.and_where(chunk::Column::Id.in_subquery(orphan_chunk_ids))

This problem takes down atticd entirely. We will submit a PR to fix this but I wanted to open this ticket for tracking purposes.