[canvaskit] Remove additional copies of CanvasKit when testing

Speculative fix for flaky test bot. My guess is that since there were
3 .spec.js that were all trying to load CanvasKit at the same time, the
browser would fail to compile/process all that WASM and timeout.

This cleans it up so there's only one copy of CanvasKit shared by all
tests.

Bug: skia:8810
Change-Id: I60a77dae93b7c3e5d45923b4af93a223ac26220c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198161
Auto-Submit: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
7 files changed