Update options to be a mapping instead of a simple namespace

[mtreinish]

Summary

This commit changes the options class to be a mapping instead of a
simple namespace. While we wanted to preserve attribute based access
primarily the simple namespace is too limited in practice and involves a
lot of hacking around the internals such as frequent calls to
Options.__dict__ to get an iterator of fields in the options. To improve
the usability of the class without breaking existing users this changes
the base class to be a MutableMapping and adds the necessary methods to
make it usable like a dict or a simple namespace.

Details and comments

[mtreinish]

Ugh, it looks like this is breaking Aer in some way and because of how the QuantumInstance runs circuits things get stuck in an infinite loop on failure causing the algorithms tests to timeout. I'll have to run this locally to debug what I messed up

[mtreinish]

This is no longer valid and was actually integrated in #5885 and then subsequently fixed in #7347 and #7353 so this no longer is necessary.