Fix/9548 auto renewal persistence

[LevinMK23]

Description

Fixes #9548

This PR fixes the auto-renewal behavior in the broker pallet to match the documented behavior.

Problem: When auto-renewal fails due to insufficient funds or other errors, the system disables the auto-renewal setting entirely, requiring manual re-enablement.

Solution: The auto-renewal setting now persists across multiple periods even when renewal attempts fail, as stated in the documentation: "Even if an auto-renewal attempt fails, the auto-renewal setting remains active for subsequent sales."

Integration

For downstream projects using pallet-broker:

• No breaking changes
• Auto-renewal will now retry automatically after failures
• Existing code continues to work without modifications

Review Notes

Changes made:

1. Modified renew_cores() in tick_impls.rs to return Some(AutoRenewalRecord) instead of None on failures
2. Updated next_renewal to sale.region_end for retry in the next period
3. Updated existing test auto_renewal_works to expect new behavior
4. Added new test auto_renewal_persists_after_failure to verify the fix

Before:

• Failed renewal → auto-renewal setting deleted

After:

• Failed renewal → auto-renewal setting preserved for next attempt

Checklist

• My PR includes a detailed description as outlined above
• My PR follows the labeling requirements (T14-system_parachains)
• I have added tests that prove my fix is effective
• PRDoc file included

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