'show readyset status' should print enablement status of dataflow flags

[gvsg-rs]

Description

It is currently tedious to find out which dataflow flags are enabled on a system unless someone looks at the logs, or the startup arguments to the Readyset binary. We should make it easy to discover configuration information through one of the 'show' commands. "show readyset status" is as fine a place as any to display this information. Alternatively, we could have a "show readyset config" as well.

I'm recommending 'show readyset status':

postgres=> show readyset status;
            name            |            value
----------------------------+------------------------------
 Database Connection        | Connected
 Connection Count           | 3
 Snapshot Status            | Completed
 Maximum Replication Offset | (246/480159D0, 246/48015A00)
 Minimum Replication Offset | (246/480159D0, 246/48015A00)
 Last started Controller    | 2024-09-06 23:38:49 UTC
 Last completed snapshot    | 2024-09-06 23:38:57 UTC
 Last started replication   | 2024-09-06 23:38:57 UTC
 dataflow flags             | full-materialization, full-mat-persistence, post-lookup.

Change in user-visible behavior

Yes

Requires documentation change

Yes