Only fire Duck Player navigational pixel for main frame navigations

[ayoy]

Task/Issue URL: https://app.asana.com/0/1203249713006009/1208836976436118/f

Description:
This change limits Duck Player navigational pixels to be sent only on main frame navigations

Steps to test this PR:
See this Asana comment for more context of the breakage.

1. Run the app from Xcode
2. Filter logs by "PixelKit" category
3. Set DuckPlayer to "always ask" mode
4. Go to youtube.com, search for video, open video page
5. Verify that refreshing doesn't trigger navigation_back or navigation_outside_youtube pixels

Definition of Done:

• Does this PR satisfy our Definition of Done?

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Internal references:

Pull Request Review Checklist
Software Engineering Expectations
Technical Design Template
Pull Request Documentation

[Bunn]

LGTM, btw, the refresh button gets disabled in duck player, so I just selected the address bar and pressed enter to force refresh

[ayoy]

@Bunn sorry, I was referring to refreshing the YouTube video page, not Duck Player.

[Bunn]

@Bunn sorry, I was referring to refreshing the YouTube video page, not Duck Player.

All good, I tested this case as well.
Refreshing youtube triggers:
m_mac_duck-player_overlay_youtube_impressions
m_mac_duckplayer_youtube_overlay_navigation_refresh

but not the ones mentioned in the description