[Internal] Transform `handle_missed_block_detection` and `handle_missed_attestations_detection` to pure function without side effet

[nalepae]

These function should not call beacon nor prometheus probes.
All information they need should be provided by the calling function.

It will also solve the issue that get_block method of beacon is called 2 times:

• One time for blocks
• One time for attestations

which is a waste of resources.