Remove strict super seeding option and consider not using super seeding altogether

[FranciscoPombal]

The very long discussion on #12162 about super seeding led to this: arvidn/libtorrent#4440

Thus, we should

1. remove the strict super seeding setting from the settings, and
2. consider not using the non-strict super seeding mechanism at all in the rest of the code base.

I expect point 1 to be more consensual.

[Seeker2]

I use the non-strict super seeding mechanism on an occasional basis, so I would greatly prefer keeping it.

[ghost]

Since it’s deprecated now, there’s no point in keeping it.
Some people might still want to use the non strict method. The use case could be when there’s a lot of peers in the swarm with only one seeder with slow upload speed.

[Seeker2]

Here's another use case:
Is there any way to block a specific client (Thunder)? #10258

[FranciscoPombal]

"Normal" super seeding is decently handled by libtorrent by default. Removal of strict super seeding happening here: #12423