[Browser Frame] Move caption/title layout to browser frame

The browser frame is responsible for laying out frame elements, and for
generally providing platform-specific layout and style information to
the browser layout.

The previous implementation of the function on BrowserWidget mostly just
called into BrowserFrameView anyway, and had a bunch of platform-
specific logic using #if BUILDFLAG.

This new implementation moves it down into BrowserFrameView, and splits
out the platform-specific code into platform-specific implementations.
It also adds a small specialization to OpaqueBrowserFrame on Windows to
share layout logic with BrowserFrameViewWin, preventing code
duplication.

Bug: 447104848
Change-Id: I75a8552242e18f47f5ba65838b526ec6963a31d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6989591
Commit-Queue: Dana Fried <dfried@chromium.org>
Reviewed-by: Eshwar Stalin <estalin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1523554}