Proto: freeze rewards under AI

BEHIND the adaptive_inflation feature flag:

Because rewards will be shared with costakers automatically through pseudo-tokens, we need to pay them on the stake pool balance rather than the baker's balance.

The following rewards are now paid on the frozen deposits balance rather than their spendable balance:

• Baking rewards
• Baking bonuses
• Endorsing rewards
• Revelation rewards

The following rewards are non-inflationary and still paid on the spendable balance:

• Transaction fees
• Denunciation rewards

Tests shouldn't be impacted yet