This change backports the PostgreSQL indexing sink, addressing part of #6828.
Development on the main branch has diverged substantially since the v0.34.x
release. It includes package moves, breaking API and protobuf schema changes,
and new APIs, all of which together have a large footprint on the mapping
between the implementation at tip and the v0.34 release branch.
To avoid the need to retrofit all of those improvements, this change works by
injecting the new indexing sink into the existing (v0.34) indexing interfaces
by delegation. This means the backport does _not_ pull in all the newer APIs
for event handling, and thus has minimal impact on existing code written
against the v0.34 package structure.
This change includes the test for the `psql` implementation, and thus updates
some Go module dependencies. Because it does not interact with any other types,
however, I did not add any unit tests to other packages in this change.
Related changes:
* Update module dependencies for psql backport.
* Update test data to be type-compatible with the old protobuf types.
* Add config settings for the PostgreSQL indexer.
* Clean up some linter settings.
* Hook up the psql indexer in the node main.