[DevTools] Propagate keyboard shortcuts in native menus.

The DevTools front-end already passes a `shortcut` field as part of the
`ShowContextMenuItem`, but the Chromium back-end never paid attention to
this field until now. With this change, we thread through the shortcut
all the way to the `RenderViewContextMenuBase` and put it as the minor
text for menu items.

Screenshot: https://i.imgur.com/8mFJsWM.png
Doc: https://goo.gle/devtools-consistent-context-menus
Change-Id: I4ce3b13f8c2445c6b658c3445af68344fde6a64d
Bug: 330213829
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5489020


Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Danil Somsikov <dsv@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1304296}