combine Trackers Blocked and Ads Blocked on NTP

[rebron]

Description

On the new tab page, Trackers Blocked and Ads Blocked should be combined into a single count and labeled appropriately. For the backend, tracking-protection lib will move into the ad-block lib so good time to simplify and relabel this metric.

Current result:

Expected result:

Single metric with label
[Count]
Ads & Trackers Blocked

[rebron]

cc: @tomlowenthal for label text for this metric.

[tildelowengrimm]

I'd like to just collapse into "Trackers blocked".

[EyanGoldman]

Question that is probably unlikely, but what happens when you get to 1M + ads blocked, do the numbers dynamically shift to make space? Is there a risk of overlapping? This is especially relevant if we are merging ads and trackers as that number will grow much faster...

[cezaraugusto]

@EyanGoldman yes, the stats row expands to fit larger numbers

[LaurenWags]

Verified passed with

Brave	0.68.118 Chromium: 76.0.3809.87 (Official Build) beta (64-bit)
Revision	111fe1e15d5ced26080a7dc239bcfe70f6c49aad-refs/branch-heads/3809@{#967}
OS	Mac OS X

• Verified with clean profile:
  
• Verified with upgraded profile. This is from 0.67.x:
  
  And after upgrading to 0.68.x the Ads/Trackers were combined as expected:
  

Verification passed on

Brave	0.68.119 Chromium: 76.0.3809.87 (Official Build) beta (64-bit)
Revision	111fe1e15d5ced26080a7dc239bcfe70f6c49aad-refs/branch-heads/3809@{#967}
OS	Windows 10 OS Version 1803 (Build 17134.523)

• Verified with a clean profile

• After upgrading to 0.68.x the Ads/Trackers were combined as expected

Verification passed on

Brave	0.68.118 Chromium: 76.0.3809.87 (Official Build) beta (64-bit)
Revision	111fe1e15d5ced26080a7dc239bcfe70f6c49aad-refs/branch-heads/3809@{#967}
OS	Ubuntu 18.04 LTS

Before upgrade

After Upgrade

Clean profile