Use unknown instead of any in type functions

[robertbrignull]

When checking if an object is a certain type, we should use unknown instead of any. The only difference this makes to the implementation is we need to add some extra obj !== null and typeof obj === "object" checks, but this makes it safer anyway since before if some of these were passed a null value they would throw an error when trying to access fields on it.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[koesie10]

Thanks!