[bazel] Point to vk_mem_alloc from DEPS

To make it easier to use the G3 version of this dep,
we make a reference to it in the WORKSPACE.bazel, so
we can refer to this external dep with the @ notation.

I would like to do this for all of our third party
deps, but one at a time.

Change-Id: I03e0beca124225e0faf1232278dae641da8a3e4d
Bug: skia:13240, skia:13211
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/535358
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
3 files changed