[ads] Notification ads are shown when playing media

[tmancey]

Resolves brave/brave-browser#38225

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[btlechowski]

Verified with

Brave	1.68.12 Chromium: 125.0.6422.41 (Official Build) nightly (64-bit)
Revision	52fd851
OS	Linux

Verified test plan from brave/brave-browser#38225

Test case 1

Verified ads are not shown when media is playing

[7096:7096:0513/220524.087539:VERBOSE2:permission_rules.cc(263)] Media is playing
[7096:7096:0513/220524.088343:VERBOSE1:notification_ad_serving.cc(77)] Notification ad not served: Not allowed due to permission rules

Test case 2

Verified ads are not shown when media is playing even when window was restored

[7096:7096:0513/220651.256893:VERBOSE2:permission_rules.cc(263)] Media is playing
[7096:7096:0513/220651.257177:VERBOSE1:notification_ad_serving.cc(77)] Notification ad not served: Not allowed due to permission rules