Make sure the CertVerifier::RequestParams hash is injective

Otherwise distinct inputs can collide and cause some mishaps.
Fortunately, the leaf certificate is reliably at the front, so it should
not be possible for someone to cause us to accept an invalid (name, key)
binding.

Bug: none
Change-Id: I8917a9d7f4e8432d8542f4d80747f54f723cf5d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5159854
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Bob Beck <bbe@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1253611}