change: Remove slot dependency from selection inherents

[AmbientTea]

Description

Removes dependency on current slot number from authority-selection-inherents and instead use epoch duration and current timestamp. This change should be backwards compatible (I am testing that).

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• The size limit of 400 LOC isn't needlessly exceeded
• The PR refers to a JIRA ticket (if one exists)
• New tests are added if needed and existing tests are updated.
• New code is documented and existing documentation is updated.
• Relevant logging and metrics added
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff