build: Add exhaustive switch statement lint

For now, only check the JSON views package, since this was the instance
that most recently tripped us up. There are a few dozen failures
elsewhere in Terraform which would need to be addressed before expanding
this to other packages.

scripts/exhaustive.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+echo "==> Checking for switch statement exhaustiveness..."
+
+# For now we're only checking a handful of packages, rather than defaulting to
+# everything with a skip list.
+exhaustive ./internal/command/views/json