Update SearchBox and use it in Project Views code

[magicznyleszek]

Description

Displays search box for My Projects and Project Views routes.

Code Review Notes

This changes a few things:

• Move MainHeader component to better directory
• Split out AccountMenu component (out of MainHeader) and change to TypeScript
• Typescriptize HeaderTitleEditor component
• Typescriptize SearchBox component
• Move searchBoxStore to MobX and update all code that was using it
• Update customViewStore to use new searchBoxStore to fetch assets filtered by search phrase

General idea is to have this searchBoxStore being the singe source of truth for search box input. Every component or store that needs to know search phrase is using it now. searchBoxStore is handling only single context at a time - that is why each piece of code that is using it, needs to register unique context id first. This is because some stores are working even after switching routes and we want to avoid unnecessary calls.

Related issues

Fixes #4063