Create UI: unit tests for everything not yet done

[severinbeauvais]

• similar to Create UI: implement new Amalgamating Businesses component - Part IV - DO THIS LAST #18641 (ting table unit tests)
• similar to Create UI: more framework changes, validation, etc (DO THIS LAST IN CREATE UI) #18689 (reg amalg unit tests)
• add unit tests specific to short-form amalgamations
• add any other useful unit tests

And specifically:

• in AmalgamationBusinessInfo.spec.ts, add tests for AmalgamationShortResources
• in AmalgamationInformation.spec.ts, add tests for AmalgamationShortResources
• in AmalgamationInformation.spec.ts, add tests for short-form amalgamations
• in AmalgamationPeopleRoles.spec.ts, add tests for AmalgamationShortResources
• in AmalgamationPeopleRoles.spec.ts, add tests for regular vs short-form amalgamations
• in AmalgamationReviewConfirm.spec.ts, add tests for AmalgamationShortResources
• in AmalgamationReviewConfirm.spec.ts, add tests for regular vs short-form amalgamations
• in AmalgamationShareStructure.spec.ts, add tests for AmalgamationShortResources