Set the maximum open connections limit in PG and MySQL target configs (#10558)

As the bulk/recursive delete will require multiple connections to open at an instance,
The default open connections limit will be reached which results in the following error

```FATAL:  sorry, too many clients already```

By setting the open connections to a reasonable value - `2`, We ensure that the max open connections
will not be exhausted and lie under bounds.

The queries are simple inserts/updates/deletes which is operational and sufficient with the
the maximum open connection limit is 2.

Fixes #10553

Allow user configuration for MaxOpenConnections

ruleguard.rules.go

@@ -438,7 +438,6 @@ func httpheaderadd(m fluent.Matcher) {
 		Suggest(`$H.Set($KEY, $VALUE)`)
 }
 
-
 func hmacnew(m fluent.Matcher) {
 	m.Match("hmac.New(func() hash.Hash { return $x }, $_)",
 		`$f := func() hash.Hash { return $x }