Allow clear reannouncement + clear scheduled CK swap

[l0r1s]

Description

• Fix migration: migrate_coldkey_swap_scheduled_to_announcements now cancels the pallet_scheduler tasks that were scheduled under the old system, preventing stale swap_coldkey calls from executing after the migration.
• New extrinsic: clear_coldkey_swap_announcement (call index 133) lets a coldkey voluntarily withdraw its own swap announcement once the reannouncement delay has elapsed.

Details

The previous migration converted ColdkeySwapScheduled entries to ColdkeySwapAnnouncements but left the original scheduled calls alive in pallet_scheduler::Agenda. This PR adds a translate_values pass that tombstones those tasks (sets them to None) while preserving all other scheduler entries in the same blocks.

The new clear_coldkey_swap_announcement extrinsic enforces two guards before removing the announcement: the caller must be the owner of the announcement, and the current block must be at or past announcement_block + ColdkeySwapAnnouncementDelay. Disputed swaps are blocked at the transaction extension level as usual.

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

If this PR introduces a breaking change, please provide a detailed description of the impact and the migration path for existing applications.

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)

Please include any relevant screenshots or GIFs that demonstrate the changes made.

Additional Notes

Please provide any additional information or context that may be helpful for reviewers.

[github-actions]

🚨🚨🚨 HOTFIX DETECTED 🚨🚨🚨

It looks like you are trying to merge a hotfix PR into main. If this isn't what you wanted to do, and you just wanted to make a regular PR, please close this PR, base your changes off the devnet-ready branch and open a new PR into devnet ready.

If you are trying to merge a hotfix PR, please complete the following essential steps:

1. go ahead and get this PR into main merged, so we can get the change in as quickly as possible!
2. merge main into testnet, bumping spec_version
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5. deploy devnet
6. merge devnet into devnet-ready

If you do not complete these steps, your hotfix may be inadvertently removed in the future when branches are promoted to main, so it is essential that you do so.

[evgeny-s]

LGTM