Add Brave Ads panel content and summary in BRewards Settings page

[jenn-rhim]

Description

The attached are the finalized Ads container content and the setting. Ads settings current contains only one control - ad notification hourly frequency.

Steps to Reproduce

Actual result:

Expected result:

Reproduces how often:

Brave version (chrome://version info)

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?
• Does it reproduce on browser-laptop?

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?
• Is the issue reproducible on the latest version of Chrome?

Additional Information

[NejcZdovc]

done in brave/brave-core#999

[LaurenWags]

@jenn-rhim can you help with a test plan for this one? Unsure what we should be looking at on 0.59.x specifically.

[NejcZdovc]

@LaurenWags for 0.59 there should be only settings page

[btlechowski]

Verification passed on

Brave	0.59.25 Chromium: 72.0.3626.53 (Official Build) beta (64-bit)
Revision	98434e6cd182d68ce396daa92e9c6310422e6763-refs/branch-heads/3626@{#620}
OS	Windows 7

Based on #1533 (comment), Ads settings page:

[srirambv]

Marking issue as Windows/Mac only as ads is not supported on Linux for now