Add setting to 'Always show bookmarks bar on New Tab Page'

[rebron]

Test plan

See brave/brave-core#2869

Description

Some users only want to see the bookmarks bar on the New Tab page and nowhere else. We need to create a preference to support this behavior. On by default -> #5781

This is a follow up to this issue: #1306 (comment) that supports the View "Always Show Bookmarks Bar" setting on every window including the New Tab page.

Design

[simonhong]

@rebron I set milestone as 0.68.x nightly because #1306 is merged into 0.68.x. I assume that many users will say about this if don't have a fix this this.

[rebron]

cc: @petemill may have suggestions on how this should look (where setting should go).

[rebron]

Can we check that with this fix, on Windows 10, bookmarks bar shows up in full screen mode?
cc: @Brave-Matt

[Brave-Matt]

Bookmarks bar spacing issue in Fullscreen mode looks like this:

As opposed to:

Occurs on Release (67.125 - nightly). User reporting same behavior:
https://www.reddit.com/r/brave_browser/comments/csix6u/bookmarks_on_new_tab_page_dont_align_well_in_full/

[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 always show bookmark bar on NTP option (Uplift 2869 to beta) brave-core#3244

Verification passed on

Brave	0.69.121 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 steps from brave/brave-core#2869
Always show bookmarks bar on New Tab page is on by default.

Verified passed with

Brave	0.69.123 Chromium: 76.0.3809.132 (Official Build) beta (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Mac OS X

• Verified test plan from Add always show bookmark bar on NTP option brave-core#2869
• Verified that Always show bookmarks bar on New Tab page is on by default per Make bookmarks bar visible on New Tabs Page by default #5781