merge_pr_49007

Add client extensions to getClientCapabilities() per WebAuthn L3 spec

https://w3c.github.io/webauthn/#sctn-getClientCapabilities

Fixed: 377366929
Change-Id: I954430fa786a9350c463a004c569d69d1e66ef73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5999316
Commit-Queue: Andrii Natiahlyi [email protected]
Reviewed-by: Adam Langley [email protected]
Cr-Commit-Position: refs/heads/main@{#1379271}