Migrate HeapSnapshotWorkerProxy away from internal singleton usage by
requiring Console in its constructor.

Bug: 493763857
Change-Id: Idf6d563149ef6284e1c25270560c7cb4b452a650
TAG=agy
CONV=d351cc2a-e81d-41ab-8b62-666d1641d26d
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/8106175
Commit-Queue: Kim-Anh Tran <kimanh@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Auto-Submit: Kim-Anh Tran <kimanh@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>