Deno execution on Windows is much slower due to WebGPU

[dsherret]

In Deno 1.38.5, a simple hello world executed in 27ms on my machine. In 1.39.0 (The return of WebGPU), it jumped to 81ms where it has remained.

Our main function runs in ~25ms, but the total execution is slower.

Tracing this in procmon, it seems startup is quick, but shutdown is slow. I'm seeing the same behaviour outlined in this stack overflow issue: https://superuser.com/questions/1507765/delay-to-return-the-prompt-control-after-executing-external-commands (I also see the GRE_Initialize value being queried)

> deno upgrade 123d9ea047a2e10803e260ebf00f31fcc98463ee
> Measure-Command { deno run V:\scratch\hello.js }
35ms
> deno upgrade 393abed3873d83019feb5bcebb10a6929133862a
> Measure-Command { deno run V:\scratch\hello.js }
91ms

• 123d9ea (Before)
• 393abed (After - WebGPU)