Revert "[infra] Switch from isolate to RBE-CAS"

This reverts commit 03d69876ff0eb33ac9ae968207a72af505b10502.

Reason for revert: failing

Original change's description:
> [infra] Switch from isolate to RBE-CAS
>
> Bug: skia:10883
> Change-Id: I4bab202c89253248b7c93d23540038f83af97d33
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/340100
> Commit-Queue: Eric Boren <borenet@google.com>
> Reviewed-by: Weston Tracey <westont@google.com>

TBR=borenet@google.com,westont@google.com

Change-Id: Idf99f74579e44bb6b88dcb2c727d8215a3c70c71
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:10883
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/341678
Reviewed-by: Eric Boren <borenet@google.com>
33 files changed