[WIP] Experiment serialization and reconstruction

This PR will able the user to save and load experiment object to the result_db. This issue was discussed in #1392

Tasks to complete this PR:

[ ] make save experiment flag to save experiment config to the result_db
[x] Add serialization of both Experiment obj, Analysis obj and figure related obj (for plotter, drawer and figure options)
[x] Use the provider to add the correct backend to the experiment object.
[ ] Make a utility function to load experiment and experiment data simultaneously.
[ ] Add tests for simple experiment loading and saving
[ ] Add tests for composite experiments, e.g. flat, nesting etc..
This feature was requested by the experimentalists.

[x] I have read the contributing guide CONTRIBUTING.md.
[ ] I have added the tests to cover my changes.
[ ] I have updated the documentation accordingly.
[ ] I have added a release note file using reno if this change needs to be documented in the release notes.

Qiskit-Extensions / qiskit-experiments