Implement user activity frequency capping

[tmancey]

Implement user activity frequency capping as a pre-requisite for ad delivery timing

[srirambv]

Verification passed on OnePlus 6T with Android 10 running 1.15.69 x64 build

• Verified ads is enabled when rewards is enabled
• Verified number of ads shows as per settings
• Verified ads is shown only when the browser is in use
• Verified view/click/landed/dismiss is logged correctly

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Verification passed on Samsung Tab A with Android 10 running 1.15.69 x64 build

• Verified ads is enabled when rewards is enabled
• Verified number of ads shows as per settings
• Verified ads is shown only when the browser is in use
• Verified view/click/landed/dismiss is logged correctly

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Verification completed using below

Brave	1.15.69 Chromium: 86.0.4240.55 (Official Build) (x86_64)
Revision	a6d625ef6f7fe8ea0675f1cf759155a05ee1be40-refs/branch-heads/4240@{#953}
OS	macOS Version 10.14.6 (Build 18G3020)

Verified scenarios outlined in brave/brave-core#6703 (comment)

Verified ad is not shown on clean profile (0points)
Verified ad is not shown when 1 new tabs are open. (1point)
Verified ad is shown when 2 new tabs are open. (2points)
Verified ad is shown only when 1 new tab is opened and the focusing of tab is changed to another tab (2points)
Verified ad is shown after opening youtube video in a new tab (2points)
Verified ad is shown after browser becomes active and enters background 2times (2points)
Verified that score is reset after browser restart
Verified ad is not shown after opening youtube video in the same tab(1point)
Verified ad delivery for max 1, 2, 3, 4, 5 ads per hour setting

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Verification passed on

Brave	1.15.69 Chromium: 86.0.4240.55 (Official Build) (64-bit)
Revision	a6d625ef6f7fe8ea0675f1cf759155a05ee1be40-refs/branch-heads/4240@{#953}
OS	Ubuntu 18.04 LTS

Verified test plan from brave/brave-core#6703 (comment)

Verified ad is not shown on clean profile (0points)
Verified ad is not shown when 1 new tabs are open. (1point)
Verified ad is shown when 2 new tabs are open. (2points)
Verified ad is shown only when 1 new tab is opened and the focusing of tab is changed to another tab (2points)
Verified ad is shown after opening youtube video in a new tab (2points)
Verified ad is not shown after opening youtube video in the same tab(1point)
Verified ad is shown after browser becomes active and enters background 2times (2points)
Verified that score is reset after browser restart
Verified ad delivery for 2 ads per hour, 3 ads per hour, 4 ads per hour and 5 ads per hour is working as expected

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Verification passed on

Brave | 1.15.69 Chromium: 86.0.4240.55 (Official Build) (64-bit)
-- | --
Revision | a6d625ef6f7fe8ea0675f1cf759155a05ee1be40-refs/branch-heads/4240@{#953}
OS | Windows 10 OS Version 1903 (Build 18362.1016)

• Verified the test plan from Implement user activity frequency capping brave-core#6703
• Verified AD are number of Ads delivered as per the Ads settings
  Verified ad is not shown on clean profile (0points)
  Verified ad is not shown when 1 new tabs are open. (1point)
  Verified ad is shown when 2 new tabs are open. (2points)
  Verified ad is shown only when 1 new tab is opened and the focusing of tab is changed to another tab (2points)
  Verified ad is shown after opening youtube video in a new tab (2points)
  Verified ad is not shown after opening youtube video in the same tab(1point)
  Verified ad is shown after browser becomes active and enters background 2times (2points)
  Verified that score is reset after browser restart