[rustmojo] Split out remotes and receivers into their own file They were in the same file before to make things easier to review, but ultimately they're separate modules that should be in their own files. Bug: 444509367 Change-Id: Ia877f34ceaf75df7af5c8a3e8cee954bd00b24e7 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7567602 Reviewed-by: Łukasz Anforowicz <[email protected]> Commit-Queue: Devon Loehr <[email protected]> Cr-Commit-Position: refs/heads/main@{#1583408} CrOS-Libchrome-Original-Commit: 8267b804f45a9d59ea9f30e116627a4eb17973f4