Add ArrayView::supspan variants to create spans with static extent

This functions match std::span api and provide concise way to create
spans with static extent. Note that most std::span constructors for
spans with static extent are explicit and thus can't be used through
braced initialization.

This change includes examples where those new functions are most
helpful.

Bug: webrtc:439801349
Change-Id: I4158ba12f28d0271fe9f9577533b2b36f3cd9222
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/450680
Reviewed-by: Evan Shrubsole <eshr@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46962}