Fix closing recordings/tables that are still being loaded showing up again

[jprochazk]

• Fixes In the web viewer, if a recording is not finished loaded, if you close it, it will reappear and begin loading again #10965
• Fixes debug_assert triggers when closing partially loaded recording #9848

To reproduce the issue, open a large partition or throttle your network speed. As it's loading, close it in the recording panel. It actually stays there and continues downloading.

The fix is to drop the receiver as well.

I also noticed that dropping the receiver doesn't immediately cancel the download, the GetChunks continues in the background according to the console network tab. We should probably look into making those requests fully cancel safe

[github-actions]

Web viewer built successfully. If applicable, you should also test it:

• I have tested the web viewer

Result	Commit	Link	Manifest
✅	761d088	https://rerun.io/viewer/pr/10963	+nightly +main

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[Wumpf]

using the flight data nightly example I confirmed that it fixes the assert 👍 (added ticket to the close list)

This fix is relevant for OSS & Cloud the same way as :)

[jprochazk]

Created a follow-up issue about request cancellation: #10967