add lint: containedctx (#1240)

Required updating connector interfaces. Bit annoying `ctx` everywhere,
but that's ultimately the correct way. Was running into context
complications in #1211 with connector being shared between activities

Putting context in struct essentially makes that struct a context, but
this is not the context we necessarily want. For more context, see
https://zenhorace.dev/blog/context-control-go

Some changes were made:
1. GetCatalog takes a context now instead of using
`context.Background()`
2. eventhubs processBatch now takes context instead of using
`context.Background()`
3. many instances of `Query`/`Exec` in snowflake/clickhouse converted to
`QueryContext`/`ExecContext`
4. got rid of cancel context in ssh tunnel, context being passed in is
sufficient

Followup to #1238

flow/.golangci.yml

@@ -3,6 +3,7 @@ run:
     - generated
 linters:
   enable:
+    - containedctx
     - dogsled
     - durationcheck
     - errcheck