Improvements to checkpointing to align it with bilby!746

See bilby!746 (merged)

1. Pickle the entire sampler
2. Save every check_point_deltaT seconds
3. Add stats and run plots at each iteration

src/parser.py

@@ -126,9 +126,9 @@ def _add_dynesty_settings_to_parser(parser):
     )
     dynesty_group.add_argument(
         "--n-check-point",
-        default=100000,
+        default=100,
         type=int,
-        help="Steps to take before checkpoint",
+        help="Steps to take before attempting checkpoint",
     )
     return parser