Add a a button to go to brave://adblock/ in the right click menu and maybe change 'Brave' name.

[ghost]

Test plan

See brave/brave-core#8394

Description

Following brave/brave-core#8156 and #14945

Then I would like to suggest a button in the menu to go to brave://adblock/ page so people who only used the old deprecated adblock feature will be able to access the rules without problem and getting lost because the "clear css" button that was removed.
I know when #8838 happens (if it is still a thing) could make things easier for some people to find where the rules are, it will be more intuitive for sure, because right now adblock page being accessible only through the 'hamburger' menu I know it is not so much for some people.

Also like the title says, maybe a change on the Brave right click menu could also be good, so reflects more it is about the adblock feature instead of being a general "Brave" that can be used for anything, unless there are plans to add more stuff to the menu that have nothing to do with Brave's adblocker, why not rename it to Brave Adblock or Brave Shields if there is more plans to add shield settings to it?

[bsclifton]

cc: @rebron @karenkliu

[stephendonner]

Verified PASSED using

Brave	1.23.68 Chromium: 90.0.4430.51 (Official Build) (x86_64)
Revision	32e5fa33a31641bded70a90e60121060691e7125-refs/branch-heads/4430@{#927}
OS	macOS Version 11.2.3 (Build 20D91)

Steps:

1. loaded cnn.com in a single tab
2. right-clicked on the page, and chose Brave -> Manage custom filters
3. confirmed I was taken to brave://adblock/ in a new tab
4. loaded cnn.com in a tab; in a 2nd tab, opened brave://adblock/
5. switched back to cnn.com tab and chose Brave -> Manage custom filters
6. confirmed I was taken back to the open brave://adblock tab
7. loaded brave://adblock/ in a single tab
8. right-clicked on the page, and chose Brave -> Manage custom filters
9. confirmed I remained on brave://adblock in the current tab

---

Verification passed on

Brave | 1.23.68 Chromium: 90.0.4430.51 (Official Build) (64-bit)
-- | --
Revision | 32e5fa33a31641bded70a90e60121060691e7125-refs/branch-heads/4430@{#927}
OS | Windows 10 OS Version 2004 (Build 19041.867)

• Verified the test plan from Add "Manage custom filters" context menu item brave-core#8394
• Ensured Brave > Manage custom filters context menu item exists and click on it navigates to a new brave://adblock tab
  
  
• Testing on adblock custom filter is covered in Update adblocking added via right-click context menu to be editable under the brave://adblock "Custom filters" section #9581 (comment)

---

Verified passed with

Brave	1.23.68 Chromium: 90.0.4430.51 (Official Build) (64-bit)
Revision	32e5fa33a31641bded70a90e60121060691e7125-refs/branch-heads/4430@{#927}
OS	Linux

Verified test plan from brave/brave-core#8394
Confirmed Brave > Manage custom filters context menu item exists and click on it navigates to a new or already opened brave://adblock tab.

[kjozwiak]

Added QA/Test-All-Platforms as right click context menu's usually differ between different platforms.