refact(cmd): Encapsulate some functionality on Command and Server

This commit extracts 3 separate pieces of functionality into their own
function/method:

- Extracts the database opening with the intention to have a function
  that performs all that functionality but returns the created database
  object rather than setting it to the Server structure.
- Extracts database validation logic, to provide a common code path for
  upcoming functionality.
- Expose schema manager on the Command struct as well as providing
  common functions to acquire shared lock/close.

internal/daemon/controller/testing.go

@@ -664,7 +664,7 @@ func TestControllerConfig(t testing.TB, ctx context.Context, tc *TestController,
 		if _, err := schema.MigrateStore(ctx, "postgres", tc.b.DatabaseUrl); err != nil {
 			t.Fatal(err)
 		}
-		if err := tc.b.ConnectToDatabase(tc.ctx, "postgres"); err != nil {
+		if err := tc.b.OpenAndSetServerDatabase(tc.ctx, "postgres"); err != nil {
 			t.Fatal(err)
 		}
 		if !opts.DisableKmsKeyCreation {