[ads] Always keep track of playing media

[btlechowski]

Currently, we keep track of playing media when ads are on, which creates problems
Since ShouldAlwaysRunBraveAdsService we can always keep track of playing media.

Steps to Reproduce

1. Clean profile
2. Enable rewards and ads
3. Turn off ads
4. Start playing a video on youtube
5. Turn on ads
6. Trigger a notification ad

Note: make media playing tracking per tab as it may happen that two or more videos are playing at the same time

Actual result:

ad is shown

Expected result:

ad is not shown because media is playing

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	1.54.74 Chromium: 115.0.5790.32 (Official Build) nightly (64-bit)
Revision	f9b78cf410ecd5b372310ef25a12ef456c77d90f-refs/branch-heads/5790@{#724}
OS	Ubuntu 18.04 LTS

cc @tmancey @aseren

[tmancey]

Blocked as discussing with @iambrianfung

[tmancey]

@iambrianfung to discuss with stakeholders

[tmancey]

This is by-design as users would only be playing audio on the other tabs, and therefore, ads should still be shown.