[native] make SingleLine the default export

Summary:
While I was working with the SingleLine component for user profiles, I noticed that this component was not default export. This is not consistent with the rest of the components in our codebase, so to address this I made SingleLine the default export and updated the import calls to reflect this change

Depends on D9013

Test Plan: flow

Reviewers: atul, inka

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9090