[native] split the inline engagement pill into two

Summary:
As a first step to redesigning the InlineEngagement component we should split the sidebar and the reactions into two separate pills. For context, this is what the new inline engagement component is supposed to look like:

This diff begins to break the chat height measurement, as such this diff and subsequent diffs won't be landed until the rest of the native inline engagement work w/ correct height measurement is completed

Linear Task: https://linear.app/comm/issue/ENG-3103/update-inlineengagement-for-native

Depends on D8496

Test Plan:
Please look at the screenshots below to see the changes

Before:

After:

Reviewers: atul, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8497