Adds new connection application name setting

[cicdw]

This PR exposes a new setting PREFECT_SERVER_DATABASE_CONNECTION_APP_NAME that allows users to specify an application name for connections opened to PostgreSQL databases. This allows us and users to hypothetically use different values for this field when running the webserver connection pools vs. the services connection pools (which are currently the same connection pool if using prefect server start but I want to experiment with a pattern where they are different).

Running SELECT application_name, datname, state, count(*) FROM pg_stat_activity group by datname, state, application_name order by count desc; let's you see this field along with how many connections the given application has.

Screenshot from running a single prefect server start command with no configuration:

Screenshot from running PREFECT_SERVER_DATABASE_CONNECTION_APP_NAME='foobartest' prefect server start:

Screenshot with another PREFECT_SERVER_DATABASE_CONNECTION_APP_NAME='xxx' prefect server start --port 4300:

[cicdw]

Also, I added these kwargs into our connection pools for non-memory SQLite as well; I couldn't find any reason why we should avoid configuring the pool for a SQLite DB.

[codspeed-hq]

CodSpeed Performance Report

Merging #16690 will not alter performance

_{Comparing add-app-name-to-conns (5bce05c) with main (3afbfb1)}

Summary

✅ 2 untouched benchmarks

[desertaxle]

LGTM! A similar setting was proposed in #16374 also, so I'm sure this will be useful to users hosting their own server!