Allow remove stake below nom minimum

[camfairchild]

Describe the bug

Currently, if you unstake to a balance below the minimum nomination stake threshold, but not exactly all your stake, it fails your SubtensorModule.remove_stake call.

However, I would expect that the stake balance should be sweep fully instead, or perhaps provide a call to allow "death" from the stake entry.

To Reproduce

1. add_stake above threshold to a delegate (e.g. 0.101 TAO)
2. remove_stake (after rate limit period) your stake so it would be below the threshold, but not 0 (e.g. 0.0011 TAO, 0.0001 TAO above)
3. FAIL! remove_stake is rejected.

Expected behavior

I would expect something more like this:

1. add_stake above threshold to a delegate (e.g. 0.101 TAO)
2. remove_stake (after rate limit period) your stake so it would be below the threshold, but not 0 (e.g. 0.0011 TAO, 0.0001 TAO above)
3. Success! (but Stake Map entry is removed, and you remove all 0.101 TAO stake)

or

1. add_stake above threshold to a delegate (e.g. 0.101 TAO)
2. remove_stake_allow_death(0.0011) (after rate limit period)
3. Success! (Stake Map entry is removed, and you remove all 0.101 TAO stake)

Screenshots

No response

Environment

OS: NA. Chain Spec: 149

Additional context

No response

[camfairchild]

Should be fixed by #383
edit: Seems to be undone by #366 here

[camfairchild]

Is fixed by #462