Brave Today publishers should be easily disabled

[petemill]

Design requirement to be able to click on any card's publisher and have a menu popup to disable that publisher.

Test plan

0. Scroll to Brave Today
1. Any Publisher name (except on a category list card) should be able to be hovered to present a button
2. Clicking the button should open a popup with 1 entry labeled "Disable content from [publisher name]"
   3.a. Clicking that popup menu entry should close the popup.
   3.b. Pressing escape should close the popup
   3.c. Clicking outside of the popup should close the popup
3. When clicking the popup menu entry, after a brief moment, the "Load New Content" blue "pill" button should appear at the top of the Viewport. Clicking should refresh the feed with the publisher's content removed.

[btlechowski]

Verification passed on

Brave	1.18.70 Chromium: 87.0.4280.101 (Official Build) (64-bit)
Revision	9407c80213cda69c2b7abcb4fa8e3f74488f4956-refs/branch-heads/4280@{#1807}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

Verified test plan from the description
Verified clicking on publisher button shown Disable Content Menu

Verified clicking that popup menu entry closes the popup.
Verified pressing escape closes the popup
Verified clicking outside of the popup closes the popup
Verified the content from given publisher is disabled
Verified clicking the popup menu entry, after a brief moment, the "Load New Content" blue "pill" button appears at the top of the Viewport

Verified clicking refreshes the feed with the publisher's content removed.

Logged #13112