Reduce frequency of discover_list_impression tracking

[ashiagr]

discover_list_episode_play event gets fired multiple times when it shouldn't be.

Example 1

This is what happens on tapping the play button on a single episode feature in the discover feed, without any scrolling interaction:

11:08:34.741 🔵 Tracked: discover_list_episode_play
11:08:34.853 🔵 Tracked: discover_list_impression
11:08:34.860 🔵 Tracked: discover_list_impression
11:08:34.885 🔵 Tracked: discover_list_impression
11:08:34.899 🔵 Tracked: discover_list_impression
11:08:34.906 🔵 Tracked: discover_list_impression
11:08:34.911 🔵 Tracked: discover_list_impression
11:08:34.967 🔵 Tracked: playback_play, Properties: {"source":"discover",...}

Example 2

After opening up one of the featured podcasts from the discover screen, tapping the subscribe button fires off the following events even though the discover screen isn't visible either before or immediately after tapping the button:

11:13:33.413  🔵 Tracked: podcast_screen_toggle_summary
11:13:33.418  🔵 Tracked: podcast_screen_subscribe_tapped
11:13:33.580  🔵 Tracked: discover_list_impression
11:13:33.586  🔵 Tracked: discover_list_impression
11:13:33.592  🔵 Tracked: discover_list_impression
11:13:33.599  🔵 Tracked: discover_list_impression

Noticed in https://github.com/Automattic/pocket-casts-android/pull/345#discussion_r984697055

Note that

• This is how we were handling the event for Firebase.
• Only the unique impressions is the main value shown to the user. (p1664575119091089-slack-C02ATC80MUM)

[mchowning]

I just got extra events when I was playing episodes from a podcast that I had added via the discover tab even though I accessed the podcast via the Podcasts tab:

1. Went to the discover screen
2. Subscribed to a podcast in the trending list by tapping the plus symbol
3. Went to the podcast's tab
4. Tapped on the podcast I just subscribed to
5. Tapped on the play icon next to one of the episodes
6. 🔴 Two discover_list_impression events were fired

The same thing happens if I play the episode via a filter.

[mchowning]

I just got extra events when I was just playing episodes from a podcast that I had added via the discover tab even though I accessed the podcast via the Podcasts tab...

I get even more extra events if I scroll a bit on the discover page first. After that, taping play or pause (on any screen, not necessarily on the discover screen) fires off even more discover_list_impression events than if I never visited the discover tab.

[mebarbosa]

@ashiagr Do you think this ticket still make sense? I tried to reproduce it, but I did not face with any weird tracking