Init-sync queue assert order and uniqueness of blocks emitted

[farazdagi]

What type of PR is this?

Feature

What does this PR do? Why is it needed?

• Duplicate blocks are filtered out.
• Unnecessary blocks stream notification removed.

Which issues(s) does this PR fix?

Fixes #5857

Other notes for review

• Redundant block requests are in core of the init-sync process: peers can provide wrong data, slot ranges need to be re-requested, and processing redone. Therefore, extra caution must be applied when filtering out blocks.
• Current implementation assumes that if processBlock function didn't end up in error, block can be considered as processed, and its slot is logged. All future requests to processBlock must be made for a higher slots.
• When implemented in Check Whether Block Is Already Processed #5850 we had an issue which is summarized by Terence as following:

Archived point is set to 256 slots
In attempt1, the node is syncing between slot 256 to 512.
The node restarts at 312, in attempt2, the node resyncs from 256 but now the node wouldn’t process the blocks between 256 to 312 anymore and that’s detrimental to new-state-mgmt

This problem will not occur with filtering at the round robin level - as on restart, slot's after the head slot will be re-checked again.

[codecov]

Codecov Report

Merging #6146 into master will not change coverage.
The diff coverage is n/a.

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  Partials     2228     2228