Issue 7633: Add new bucket to ads/rewards p3a metrics. (uplift to 1.4.x)

[brave-builds]

Uplift of #4414
Fixes brave/brave-browser#7633

Approved, please ensure that before merging:

• You have checked CI and the builds, lint, and tests all pass or are not related to your PR.
• You have tested your change on Nightly.
• The PR milestones match the branch they are landing to.

After you merge:

• The associated issue milestone is set to the smallest version that the changes is landed on.

[kjozwiak]

Linux failed due network-audit failing as per https://ci.brave.com/job/brave-browser-build-pr/job/pr4414_ie_p3a_ads_fix_1.4.x/1/execution/node/357/log/. However, it's a known issue and will be addressed via brave/brave-browser#7207.

macOS failed due to test-install as per https://ci.brave.com/job/brave-browser-build-pr/job/pr4414_ie_p3a_ads_fix_1.4.x/1/execution/node/706/log/. However, it's a known issue and not related this specific PR.

[kjozwiak]

Uplift into 1.4.x approved after deliberating with @brave/uplift-approvers. As per #4627 (comment), network-audit on Linux failed due to ENOAUDIT and macOS failed due to test-install which are known issues and not specific to this PR.

Please make sure that the correct labels are being used and the associated issue is moved into the correct milestones.