Add new 'Simple View' for Shields

[rebron]

Test plan

See brave/brave-core#2874

Description

Show a "Simple view" on Shields which will be the global default view for all users. The colors and fonts should be the same as what already exists in the Shields panel.

Design

User Flows

Abtract link for more CSS and plain text: https://share.goabstract.com/346f8cac-0c8f-4ebf-b76f-716a92e6c05b

[tildelowengrimm]

Karen is going to come through with some slightly-updated designs which mach the typeface weights and colors from #1956.

[srirambv]

Verification passed on

Brave	0.69.119 Chromium: 76.0.3809.132 (Official Build) beta (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Linux

• Verified test plan from Add support for multiple views on Shields brave-core#2874
• Verified one time message is shown
  
• Verified advance view is retained between pages after dismissing the notification
• Verified simple view is retained between pages if advance view is never clicked or changed in settings

Verification passed on

Brave	0.69.119 Chromium: 76.0.3809.132 (Official Build) beta (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Windows 7 Service Pack 1 (Build 7601.24494)

• Verified test plan from Add support for multiple views on Shields brave-core#2874
• Verified if modes persists between browser restart
• Verified the chosen mode is retained between pages
  
  

Verification PASSED on macOS 10.14.6 x64 using the following build:

Brave	0.69.130 Chromium: 77.0.3865.90 (Official Build) (64-bit)
Revision	58c425ba843df2918d9d4b409331972646c393dd-refs/branch-heads/3865@{#830}
OS	macOS Version 10.14.6 (Build 18G95)

• ensured that Simple View was being used as default view with new profiles
• ensured that the warning message appears when switching to Advanced View via the shields panel or brave://settings
• ensured that Simple View or Advanced View globally for every tab opened
• ensured that the settings persisted after several browser restarts
• ensured that you can disable/enable shields without any issues (changing the views via brave://settings during disabled states)
• Upgraded 0.68.142 CR: 77.0.3865.90 --> 0.69.130 Chromium: 77.0.3865.90 and ensured the above cases worked without issues
• Reproduced existing users getting warning message when opening shields for the first time - follow up to 5582 #5924 which was labelled as Wontfix