[Views] Rename high efficiency to memory saver in Views

This is one of a set of CLs to rename the "high efficiency" feature to
"memory saver" to match the branding we launched with and resolve
confusion when searching for code. All CLs are tagged with
#rename-high-efficiency. I plan to wait for most of them to be
approved before starting to submit these changes to ensure the code
remains in a consistent state. After submitting these CLs I'll make
another pass to capture any remaining references that can be changed.

#rename-high-efficiency

Bug: 1493843
Change-Id: I3250707e8b1102e09181916c89caab62f91ff23a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5082886
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Peter Boström <pbos@chromium.org>
Reviewed-by: Eshwar Stalin <estalin@chromium.org>
Commit-Queue: Alison Gale <agale@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1236023}