feat(youtube): support channel search extraction

[Priveetee]

This adds the extractor side for YouTube channel search.

It supports URLs like:

https://www.youtube.com/@somechannel/search?query=test

and also:

https://www.youtube.com/channel/UC.../search?query=test

The extractor now keeps the search query in the clean URL and sends it to YouTube in the channel browse request, so different searches from the same channel don't get mixed together.

For the client side, honestly I had 0 inspiration on how to implement it properly for now, so I kept this PR extractor-only instead of adding some random half-baked UI.

So this does not add the full visible feature in the app yet. It only makes the extractor able to load the results once the client has a way to call it.

I also didn't add search as a normal channel tab, because unlike videos/shorts/playlists it needs a query from the user before it can do anything.

Supported query params:

• query
• search_query
• q

Refs InfinityLoop1308/PipePipe#1350

Tested:

• git diff --check
• compileJava
• compileTestJava
• local checks with handle URLs
• local checks with channel ID URLs
• query aliases
• encoded queries with spaces
• empty/no-result searches
• existing videos/shorts/playlists/livestreams tabs
• channel search pagination