[New] serialize ODEScenario object

[lisphilar]

Summary of this new feature

Serialize ODEScenario object. This is related to #741 regarding deprecated Scenario class.
We can skip building baseline scenario when we have saved JSON file.

(Optional) Solution with the current version

import covsirphy as cs
filer = cs.Filer(directory="input", prefix="jpn")
snr_build = cs.ODEScenario.auto_build(geo="Japan", model=cs.SIRFModel)
# Dump
json_file = snr_build.to_json(**filer.json(title="scenarios"))
# Restore
snr = cs.ODEScenario.from_json(json_file)
# Check
snr_build == snr
snr.summary()

CovsirPhy version I used: 2.27.1

[lisphilar]

Documentation will be updated later.

[lisphilar]

With #1257,

• update documentation
• remove ODEScenario.__eq__ and ODEScenario.__ne__ because they are unstable