Remove stats usage ping disabled by policy pref, rename policy

[DJAndries]

brave/brave-browser#48187

[brave-builds]

Warning

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components/brave_stats/browser/brave_stats_updater_util.h: PrefService forward declaration is no longer needed

[brave-builds]

Warning

You have got a presubmit warning. Please address it if possible.

Discovered possible removal of preference registrations.

Please make sure to properly deprecate preferences by clearing their
value for a couple of milestones before finally removing the code.
Otherwise data may stay in the preferences files forever. See
Migrate*Prefs() in chrome/browser/prefs/browser_prefs.cc and
chrome/browser/prefs/README.md for examples.
This may be a false positive warning (e.g. if you move preference
registrations to a different place).

Items:

browser/brave_stats/brave_stats_updater.cc: -  registry->RegisterBooleanPref(kStatsReportingDisabledByPolicy, false);

[bridiver]

ok, after some discussion with @bbondy I think I understand what we're doing here now. I thought we were using brave origin to set the managed pref value, but the two things are independent so ideally we really would have split them into two PRs. Still working through some details to figure out what makes the most sense here

[bsclifton]

++

[brave-builds]

Warning

You have got a presubmit warning. Please address it if possible.

Found 3 lines longer than 80 characters (first 5 shown).

Items:

browser/resources/settings/brave_data_collection_page/brave_data_collection_page.ts, line 102, 86 chars
browser/resources/settings/brave_data_collection_page/brave_data_collection_page.ts, line 113, 86 chars
browser/resources/settings/brave_data_collection_page/brave_data_collection_page.ts, line 118, 97 chars

[brave-builds]

A Storybook has been deployed to preview UI for the latest push