Fix #2411: finalize_all_subnet_root_dividends has unbounded iteration over all hotkeys

[0xRozier]

Description

Replace unbounded iter_keys().collect::<Vec<_>>() in
finalize_all_subnet_root_dividends with StorageMap::translate(),
which iterates entries one at a time without allocating all keys in
memory. Empty RootClaimable entries are also cleaned up.

Related Issue(s)

• Closes finalize_all_subnet_root_dividends has unbounded iteration over all hotkeys #2411

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

N/A

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

N/A

Additional Notes

N/A

[0xRozier]

Hi, @l0r1s , @sam0x17 , @shamil-gadelshin , @JohnReedV , sorry to ping you all but can someone check this ?

[0xRozier]

@l0r1s Friendly bump — this PR fixes the unbounded memory allocation reported in #2411 by replacing collect::<Vec<_>>() with translate(). The change is small (~20 lines + tests), all checks pass, and the PR body now follows the repo template. Would appreciate a review when you get a chance. Thanks!

[l0r1s]

Suggested change

	RootClaimable::<Test>::get(hotkey_single).is_empty(),
	!RootClaimable::<Test>::contains_key(hotkey_single),

[l0r1s]

Looks good to me. Thanks.

[gztensor]

For optimization purposes, translate_values is more efficient because it skips all key decoding work, so the optimal code would be something like:

RootClaimable::<T>::translate_values::<BTreeMap<NetUid, I96F32>, _>(|mut claimable| {
    claimable.remove(&netuid);
    (!claimable.is_empty()).then_some(claimable)
});

[0xRozier]

Thanks for the reviews! I've applied both suggestions — switched to translate_values and updated the test assertion to
use contains_key.