[FedCM] Update web-visible "WebID" strings to "FedCM"

This patch updates the following reference of "WebID":
- JS exception description strings
- .well-known/webid path
- 'Sec-WebID-CSRF' forbidden request header

Bug: 1260415
Change-Id: I037e84be418c44aa79531d51b3fc99374c09c0da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3330583
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Charles Reis <creis@chromium.org>
Reviewed-by: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#951252}