[crd host] Trim down CREDITS.txt

It seems CREDITS.txt includes all 3P dependencies in Chromium, which
results in pretty large size, 14.8 MB. This CL updates how the file is
generated so that it only includes 3P dependencies of
`remoting_me2me_host_archive`. This effectively reduces the size of
CREDITS.txt to 717K on Mac.

Bug: 410045108
Change-Id: I72c846562bba0df8cbf6148bb74b1aaefbe15b8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6455781
Auto-Submit: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Lambros Lambrou <lambroslambrou@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1446846}