bft: use post-housekeep state for PoS threshold

[libotony]

Description

Ticket vechain/protocol-board-repo#1113

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• New and existing E2E tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 56.25000% with 70 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
bft/engine.go	56.98%	25 Missing and 15 partials ⚠️
cmd/thor/resync_bft.go	0.00%	12 Missing ⚠️
cmd/thor/main.go	0.00%	6 Missing ⚠️
cmd/thor/node/block_exec.go	50.00%	2 Missing and 3 partials ⚠️
bft/justifier.go	83.33%	2 Missing and 2 partials ⚠️
bft/persist.go	81.81%	2 Missing ⚠️
cmd/thor/reprocess/reprocess.go	0.00%	1 Missing ⚠️

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