[FspCache] Pass CLOUD_FILE_INFO onwards via the request metadata struct

CL:5343674 added the CloudFileInfo dictionary to the FSP API. This is
the first of a multiple CLs to start plumbing the values through the
API. This updates the METADATA to send the field to the underlying FSP
if requested and updates the function parameters calling style to
adhere to the style guide: go/cstyle#Function_Argument_Comments

Bug: b/330089398
Test: *FileSystemProviderOperationsGetMetadataTest*
Change-Id: I40c1190f8475942ee2ec5892fd662cd8ccdb6b19
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5395069
Reviewed-by: Cassy Chun-Crogan <cassycc@google.com>
Commit-Queue: Ben Reich <benreich@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1278131}