weak subjecitivity checks

[g11tech]

Motivation

The aim of the PR is to rectify weak subjectivity checks:

• while intializing if DB's finalized is ahead of the provided anchor states finalized (though wssStateFile), use the db's finalized as anchor state instead of again starting from the wss checkpoint
• add a simpler check on wss's subjectivity period of the anchor state w.r.t. the clockSlot while initializing the chain
  Description

UPDATE:
previous resolution of making the wss check on the head when chain syncs to synced state for the first time was deemed overkill, so reverted that and replaced with the initialization time clockEpoch check.

example error of providing an checkpoint wss subjectivity period behind the clockEpoch

Closes #issue_number
partially closes #3385
Steps to test or reproduce

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Codecov Report

Merging #3391 (f068176) into master (aafc5d7) will not change coverage.
The diff coverage is n/a.

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stale