FIO-8778: add case for map component model type in filter; add tests

[brendanbond]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-8778

Description

The filter process was not accounting for "map" model types, which resemble "object" model types but crucially don't have child components (or at least, child components that get iterated into). This PR updates the getModelType function to account for the "map" model type.

Breaking Changes / Backwards Compatibility

n/a

Dependencies

n/a

How has this PR been tested?

Added some automated tests.

Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above