storage/blob: Implement usability test using go-imap-backend-tests and go-imap-sql

Blob storage would also benefit from stress
testing and concurrency consistency tests.

But these are things that are probably also
worth adding to go-imap-backend-tests instead.

internal/storage/blob/test_blob_nosqlite.go

@@ -0,0 +1,13 @@
+//+build !cgo no_sqlite3
+
+package blob
+
+import (
+	"testing"
+
+	"github.com/foxcpp/maddy/framework/module"
+)
+
+func TestStore(t *testing.T, newStore func() module.BlobStore, cleanStore func(module.BlobStore)) {
+	t.Skip("storage.blob tests require CGo and sqlite3")
+}