[Nearby Presence] Add metrics for credential upload reliability

Adds metrics for the overall success of uploading credentials to the NP
server, NearbyHttpResult of each attempt to upload credentials, and the
attempt count of uploads before success.

Bug: b/276642472
Change-Id: I4c2e362225dafd0b7c014caefea429d828f03f30
Tested: Verified on DUT via chrome://histograms and unit tests
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4678293


Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Juliet Lévesque <julietlevesque@google.com>
Cr-Commit-Position: refs/heads/main@{#1180447}