Refactor czi_hosted and server into backend directory, pull common code into backend/common, refactor tests (#2102)

* move local_server -> backend/server server-> backend/czi_hosted, pull common code into backend/common update imports, tests and make commands

backend/test/decode_fbs.py

@@ -0,0 +1,31 @@
+"""
+Code to decode, for testing purposes, the flatbuffer encoded blobs.
+
+This code will need to be updated if fbs/matrix.fbs changes. For more information, see fbs/matrix.fbs and
+server/data_common/fbs/
+"""
+
+import backend.common.fbs.NetEncoding.Matrix as Matrix
+from backend.common.fbs.matrix import deserialize_typed_array
+
+
+def decode_matrix_FBS(buf):
+    """
+    Given a FBS Matrix, return an decoded Python dict containing same info in native format.
+    NOTE / TODO: row_idx not currently implemented
+    """
+    df = Matrix.Matrix.GetRootAsMatrix(buf, 0)
+    n_rows = df.NRows()
+    n_cols = df.NCols()
+
+    columns_length = df.ColumnsLength()
+
+    decoded_columns = []
+    for col_idx in range(0, columns_length):
+        col = df.Columns(col_idx)
+        tarr = (col.UType(), col.U())
+        decoded_columns.append(deserialize_typed_array(tarr))
+
+    cidx = deserialize_typed_array((df.ColIndexType(), df.ColIndex()))
+
+    return {"n_rows": n_rows, "n_cols": n_cols, "columns": decoded_columns, "col_idx": cidx, "row_idx": None}