feat(meta): add meta command for viewing/modifying key metadata

testdata/meta-ttl.ct

@@ -0,0 +1,11 @@
+# Set TTL on a key, then view it (just verify no error, can't match dynamic time)
+$ pda set hello@mt world
+$ pda meta hello@mt --ttl 1h
+
+# Clear TTL with --ttl never
+$ pda set --ttl 1h expiring@mt val
+$ pda meta expiring@mt --ttl never
+$ pda meta expiring@mt
+  key: expiring@mt
+  secret: false
+  expires: never