Reduce interval between P3A pings from ~1 hour to ~1 minute

[davidtemkin]

Test plan

See #8084 (comment)

Description

Currently P3A pings are separated by about an hour, with some randomness added.

Following a discussion about needing to retain the property that a given browser's pings cannot be linked/associated, the decision was made to reduce the interval between pings to 1 minute (assume with equivalent added randomness to reduce linkability)

[iefremov]

Fixed in brave/brave-core#4531

[iefremov]

For QA:

1. Launch the browser on a clean profile
2. Check chrome://local-state, find p3a section
3. Wait for some time, refresh, random p3a values should be marked as sent one per minute

The same can be checked on existing profile by launching the browser with --p3a-rotation-interval-seconds=5, waiting for some time (ten seconds), closing the browser - to clear sent status of recorded p3a values.

[GeetaSarvadnya]

Verification passed on

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the test plan from Reduce interval between P3A pings from ~1 hour to ~1 minute #8084 (comment)
• Verified the existing profile without using the flag --p3a-rotation-interval-seconds=5
  confirmed from @iefremov that flag should not be used when launching an upgraded profile [P3A] Sent status is not recorded on upgrade [Follow up to #8084] #8295 (comment)
• Verified that local-state file is showing sent =True and timestamp is shown for brave stats in a clean profile
  
• Verified that local-state file is showing sent =True and timestamp is shown for brave stats in an upgraded profile
  

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Verification passed on

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	Linux

• Verified test plan from Reduce interval between P3A pings from ~1 hour to ~1 minute #8084 (comment)
• Verified random P3A values is sent after a min
• Verified updating a feature state and reloading the local state file shows the changed value instantly or after 1min
• Verified on clean and upgrade sent=True and timestamp is shown
  

Verified passed with

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified test plan from Reduce interval between P3A pings from ~1 hour to ~1 minute #8084 (comment)
• Verified random P3A values is sent after a min
• Verified that local-state file is showing sent =True and timestamp is shown for brave stats in a clean profile

• Verified that local-state file is showing sent =True and timestamp is shown for brave stats in an upgraded profile