Fix tab not being inserted when opening in new tab

[CrisBarreiro]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1203249713006009/task/1210059188286306?focus=true

Description

Fix Duck Player video not being shown because of:

1. In TabsRepository we were using postValue instead of setValue, and therefore in some cases the new value was not emitted in time
2. This X post generates a temporary intermediate tab when clicking the link, that then launches the Duck Player video on a new tab. This intermediate tab has no URL, and therefore when the Duck Player tab is inserted via addAndSelectTab (which removes tabs with null URL as the first step), insertion fails because of a foreign key violation (sourceTabId doesn't exist anymore)

Steps to test this PR

Feature 1

• Go to Feature flags inventory and make sure both tabInsertionFixes and swipingTabs are enabled
• Restart the app
• Set Duck Player to "Always"
• Open this X post: https://x.com/tdinh_me/status/1909223312053657730
• Click on the YouTube link shared in the X post
• Check the video is opened in a new tab

Feature 2

• Go to Feature flags inventory and make sure both tabInsertionFixes is enabled and swipingTabs is disabled
• Restart the app
• Set Duck Player to "Always"
• Open this X post: https://x.com/tdinh_me/status/1909223312053657730
• Click on the YouTube link shared in the X post
• Check the video is opened in a new tab

[CrisBarreiro]

• Fix tab not being inserted when opening in new tab #6178 👈 (View in Graphite)
• develop

This stack of pull requests is managed by Graphite. Learn more about stacking.

[0nko]

I've tested both flows and both create new tabs, however, I've noticed a couple of things:

1. I know this is not directly the result of this PR, but it's now a consequence of opening the video in a new tab -- when pasted the "x.com" link and then clicked on the video, this did not trigger the normal webview preview update of the previous tab (see screenshot at the top left tab).

2. When I tested the 2nd flow without tab swiping, I noticed that clicking on the video actually opened 2 new tabs, one with the video and another empty tab with "t.co" URL (bottom left in the 2nd screenshot). Do you know why that might be the case?

Anyway, I'm pre-approving this and you can decide what to do. Nice work! 🥇

[CrisBarreiro]

@0nko, first issue is fixed