Remove built-in validation option

Previously, Litestream had a validator that worked most of the time
but also caused some false positives. It is difficult to provide
validation from with Litestream without controlling outside processes
that can also affect the database. As such, validation has been moved
out to the external CI test runner which provides a more consistent
validation process.

db_test.go

@@ -112,51 +112,6 @@ func TestDB_UpdatedAt(t *testing.T) {
 	})
 }
 
-// Ensure we can compute a checksum on the real database.
-func TestDB_CRC64(t *testing.T) {
-	t.Run("ErrNotExist", func(t *testing.T) {
-		db := MustOpenDB(t)
-		defer MustCloseDB(t, db)
-		if _, _, err := db.CRC64(context.Background()); !os.IsNotExist(err) {
-			t.Fatalf("unexpected error: %#v", err)
-		}
-	})
-
-	t.Run("DB", func(t *testing.T) {
-		db, sqldb := MustOpenDBs(t)
-		defer MustCloseDBs(t, db, sqldb)
-
-		if err := db.Sync(context.Background()); err != nil {
-			t.Fatal(err)
-		}
-
-		chksum0, _, err := db.CRC64(context.Background())
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		// Issue change that is applied to the WAL. Checksum should not change.
-		if _, err := sqldb.Exec(`CREATE TABLE t (id INT);`); err != nil {
-			t.Fatal(err)
-		} else if chksum1, _, err := db.CRC64(context.Background()); err != nil {
-			t.Fatal(err)
-		} else if chksum0 == chksum1 {
-			t.Fatal("expected different checksum event after WAL change")
-		}
-
-		// Checkpoint change into database. Checksum should change.
-		if err := db.Checkpoint(context.Background(), litestream.CheckpointModeTruncate); err != nil {
-			t.Fatal(err)
-		}
-
-		if chksum2, _, err := db.CRC64(context.Background()); err != nil {
-			t.Fatal(err)
-		} else if chksum0 == chksum2 {
-			t.Fatal("expected different checksums after checkpoint")
-		}
-	})
-}
-
 // Ensure we can sync the real WAL to the shadow WAL.
 func TestDB_Sync(t *testing.T) {
 	// Ensure sync is skipped if no database exists.