refactor: Convert Task Manager to use Components

This currently behaves the same as it did before: It still recreates the
table contents every half a second. It should also look identical,
though it's possible I missed some small differences.

The component structure is:

TaskManagerTable
- Table
  - TaskManagerRow
  - TaskManagerRow
  - TaskManagerRow
  - ...

TaskManagerRow is implemented so that we can later move to modifying
them in place as the process tree changes, instead of having to replace
them all.

Otherwise, most of the code is just moved around, and not changed much.

Author: AtkinsSJ