Refactor CustomForm::SubmittedAnswer to FormAnswer

[kasugaijin]

** You can start this but one of the associations cannot be made until this PR is merged (which is close) https://github.com/rubyforgood/pet-rescue/pull/856/files**

After some small architectural decisions requiring changes, we need the SubmittedAnswer model to be removed from the CustomForm scope and renamed to FormAnswer. We also need the submitted_answers table to be named form_answers. Also, please update all references to the class name and methods throughout the code. Basically a find and replace exercise for part of this work.

We should also update the associations on the model:

• has_one :organization, through: :submission
• Get rid of belongs_to :question
• Get rid of has_one :form, through: :question
• Belongs_to FormSubmission (blocked until above PR merged)

[Gabe-Torres]

Can I take this one?

[kasugaijin]

@Gabe-Torres all yours!

[kasugaijin]

@Gabe-Torres quick update - I think we should stick to using acts_as_tenant(:organization) here (like we do on all other records) instead of making a belongs_to org through submission.

[github-actions]

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