[web] Introduce thread top bar

Summary:
Introduced thread top bar component with thread name, ancestors (in the following diff) and settings menu on the right.

Test Plan: Compared result with design in figma and confirmed, that it is displayed correctly for all threads.

Reviewers: palys-swm, benschac, atul, ashoat

Reviewed By: palys-swm, benschac, ashoat

Subscribers: ashoat, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3147