…19371)

Accessing the database during debugging currently requires either
spinning up a separate PostgreSQL instance or inspecting memory to
retrieve the DSN—both of which add unnecessary friction. While the test
suite already provisions a database by default, connecting to it for
manual inspection or debugging is not straightforward.

This change introduces a clearer and more accessible way to surface the
DSN during debugging sessions, allowing developers to connect to the
test database directly without relying on external infrastructure or ad
hoc methods.

Expected Usage:
1. Debug using dlv or the IDE.
2. Step through line by line and determine that a query isn't doing what
you'd expect
3. No further insight to be gained at the Go level
4. The next place to test is to connect directly to the database while
it is in the exact state that the test has produced just before running
the query
5. Rerun the test with this option enabled and your breakpoint set right
before the questionable query runs
6. Connect to the database and inspect or troubleshoot as you need to

…19373)

Fixes #19372

We increase the read limit to 4MiB (we use this limit elsewhere). We
also make sure to stop sending messages when `containersCh` becomes
closed.