feat!: add gks support for oncogenic assertions

[korikuzma]

close #217

• CivicGksAssertion -> CivicGksClinSigAssertion
• Add CivicGksOncogenicAssertion to support CIViC oncogenic assertions
• Add back create_gks_record_from_assertion (which was removed in feat!: apply va-spec amp/asco/cap changes to gks exporter #223)

[korikuzma]

Due to ClinVar submissions only allowing the assertion criteria to be applied to all submissions, regardless of type, @susannasiebert suggested the following:

I think we need to be able to supply a parameter to the civicpy create-gks-json command to swap between onco and clinical significance submissions
maybe have it default to clinical significance and then we need to make changes on the civic server side to also kick off a submission for oncogenic

@korikuzma to add this before opening PR for review.

[korikuzma]

TODO:

• If statement proposition and evidence line proposition are the same, don't include in evidence line proposition.