Filer - conversion filing updates

[argush3]

Update conversion filing processor to populate appropriate data according to new data model.

TODOs

• Do work in legal name branch
• Use Filer - change of registration updates #18501 PR as change of registration filing is similar to conversion filing
  It may be the case that only the corps code is fine as is and only the firms code needs updating. Whoever works on this will need to dig into this.
• Add/update tests as appropriate

[jdyck-fw]

Whomever picks this up will need to follow the new way of processing filings.

[argush3]

@kzdev420 this can just move to done. We will test legal name updates at the end.