Description of problem:

The RPC api.Registry/GetBundleForChannel is consumed only by
package-server and by declarative index conversion. Neither reads any
field other than CsvName and CsvJson. The package-server generates one
call to this RPC per channel per package per catalog and is
responsible for needlessly large CPU utilization and resident set
sizes on registry pods. Removing the additional per-request processing
and database queries that populate unused fields makes the registry
server better able to absorb the bursty load from package-server.

Version-Release number of selected component (if applicable): 4.9

How reproducible: Always

Steps to Reproduce:

1. extract the certified registry database:

$ docker cp $(docker create registry.redhat.io/redhat/certified-operator-index:v4.9):/database/index.db certified.db

2. serve the extracted content:

$ opm registry serve -d certified.db

2. install ghz (https://ghz.sh/docs/install)
3. run a benchmark:

$ ghz -d '{"pkgName":"mongodb-enterprise","channelName":"stable"}' --insecure --concurrency=50 --duration=10s --call=api.Registry/GetBundleForChannel localhost:50051

Expected results: Significantly more requests should be completed during the benchmark (on my machine the number increased by more than 4x).