Consolidate page zoom limits and conversions in blink/public/

We have the min/max page zoom factors limits and methods to convert
between "page zoom factor" and "page zoom level" in
- content/common/page_zoom.h
- blink/renderer/core/exported/web_view_impl.cc
- blink/public/web/web_view.h

Instead of duplicating the limits and the logic, consolidate it all
into a single blink public header. content/browser/ and components
are able to include blink public headers, they just can't link against
blink.

The new site is in blink/public/common/page/page_zoom.h

This updates all callers to point to this common site, and removes
the redundant ones in content/common/ and WebView{Impl}.

R=dcheng@chromium.org
TBR=darin

Bug: 419087
Change-Id: Ib89f022d96c9ac7ebfd4b84c08f666a25458725a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1814857
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: Darin Fisher <darin@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Auto-Submit: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699424}