[#887] node: Drop badger writecache implementation

Badger implementation isn't tested and works not well,
but requires human resources to maintain.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/writecache/util.go

@@ -0,0 +1,20 @@
+package writecache
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"time"
+
+	"go.etcd.io/bbolt"
+)
+
+// OpenDB opens BoltDB instance for write-cache. Opens in read-only mode if ro is true.
+func OpenDB(p string, ro bool, openFile func(string, int, fs.FileMode) (*os.File, error)) (*bbolt.DB, error) {
+	return bbolt.Open(filepath.Join(p, dbName), os.ModePerm, &bbolt.Options{
+		NoFreelistSync: true,
+		ReadOnly:       ro,
+		Timeout:        100 * time.Millisecond,
+		OpenFile:       openFile,
+	})
+}