Integrate Processor Arch into stats ping

[keur]

Have brave_stats send processor architecture and make use of the API exposed in brave/brave-core#7954 if ads are enabled.

[btlechowski]

Added QA/Test-All-Platforms different platforms may have different ways of obtaining arch.

[stephendonner]

Verified FIXED using

Brave	1.22.51 Chromium: 89.0.4389.72 (Official Build) beta (x86_64)
Revision	3f345f156bfd157bd1bea06310e55f3fb2490359-refs/branch-heads/4389@{#1393}
OS	macOS Version 11.2.2 (Build 20D80)

1. clean profile, launched Brave
2. enabled Ads via Start using Rewards button
3. let time (48 hours) elapse
4. launched Charles Proxy
5. re-launched Brave
6. examined network traffic from https://laptop-updates.brave.com

Verified that &arch=X86_64 is appended to the usage ping here: https://laptop-updates.brave.com/1/usage/brave-core?platform=osx-bc&channel=beta&version=1.22.51&daily=true&weekly=false&monthly=false&first=false&woi=2021-03-01&dtoi=2021-03-03&ref=BRV001&adsEnabled=true&arch=x86_64

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Verification passed on

Brave	1.22.53 Chromium: 89.0.4389.72 (Official Build) beta (64-bit)
Revision	3f345f156bfd157bd1bea06310e55f3fb2490359-refs/branch-heads/4389@{#1393}
OS	Ubuntu 18.04 LTS

Clean profile:

After 48h

Rest of the testing done in https://github.com/brave/internal/issues/755#issuecomment-790923797

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Verification passed on

Brave | 1.22.56 Chromium: 89.0.4389.72 (Official Build) dev (64-bit)
-- | --
Revision | 3f345f156bfd157bd1bea06310e55f3fb2490359-refs/branch-heads/4389@{#1393}
OS | Windows 10 OS Version 2004 (Build 19041.804)

Clean profile:

After 48h

Additional testing is covered in brave/internal#755 (comment)

[kjozwiak]

@brave/legacy_qa there's additional STR/Cases that we'll need to run through via https://github.com/brave/internal/issues/755. Please add the verifications for those cases inside https://github.com/brave/internal/issues/755 similar to what we did with https://github.com/brave/internal/issues/751#issuecomment-775734983 👍