Prompt dialog to confirm protocol handlers registered by extensions

This CL implements the UI logic of the permission management for
protocol handlers registered by extensions though the
'protocol_handlers' Manifest Key. These handlers are under an
'unconfirmed' state, as explained in the corresponding design doc [1]
and the user must grant permission in order to use them when processing
navigation requests.

The design document has a section [1] about the Permission Management
where this logic is described. The picture [2] shows screenshots of the
new UI dialog.

[1]https://docs.google.com/document/d/1e6mSsbjLqBd1_4EAS_AX543vy53oq8SlycNwQ0mZ46g/edit?usp=sharing
[2]https://drive.google.com/file/d/1MnvehSz58-5wW1jPwsnbstqr3bg2q4Xc/view?usp=sharing

Bug: 40482153
Change-Id: Ice98f7453687d6b24c941d82ea6ad264b1de9d65
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7031939
Reviewed-by: Emilia Paz <emiliapaz@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Javier Fernandez <jfernandez@igalia.com>
Reviewed-by: Antonio Sartori <antoniosartori@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1572412}