style: renames testdata so tests can actually be parsed at a glance

testdata/import-drop.ct

@@ -0,0 +1,9 @@
+$ pda set existing@idr keep-me
+$ pda set other@idr also-keep
+$ fecho dumpfile {"key":"new","value":"hello","encoding":"text"}
+$ pda import idr --drop --file dumpfile
+  ok  restored 1 entries into @idr
+$ pda get new@idr
+hello
+$ pda get existing@idr --> FAIL
+FAIL  cannot get 'existing@idr': no such key