Owner Alpha Stake Updates

[JohnReedV]

Summary

This PR updates subnet registration so the new subnet is initialized from a pre-registration median subnet alpha price snapshot, while the registration lock is retained in the subnet reserve instead of being mostly recycled.

Previously, subnet registration only:

• locked the registration TAO,
• seeded the new subnet pool with network_min_lock,
• initialized the pool at a 1:1 reserve ratio,
• recycled the remainder.

The owner did not receive any initial alpha stake from the registration flow.

With this change:

• the current median subnet alpha price is snapshotted before the new subnet is created,
• the subnet TAO reserve is set to max(registration_lock, network_min_lock),
• the subnet alpha reserve is sized from that TAO reserve at the snapshotted median price,
• the owner receives separately minted staked alpha at that same median price,
• and the recycled registration TAO is now normally zero.

In one line:
Registering a subnet now retains the registration lock in the subnet reserve, opens the subnet at the median subnet alpha price, and grants the owner initial staked alpha priced off that same median.

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[open-junius]

It is much easier to understand if we set total_pool_tao, owner_alpha_tao_equivalent and tao_recycled_for_registration in the if/else statement.