Offline operator detections: Reduce the tau from 1% to 0.5%

[vedhavyas]

Further reduce the tau from 1% to 0.5% to be little lenient towards offline operator detection. We initially started with 1% to test out the offline detection mechanism but turns out 1% tau was a bit too strict leading to many false positives on both chronos and mainnet.

Reducing the tau to 0.5% and should Ideally be a much better guage for offline operator detection with reduced false positives.

Tests are updated to use 0.5% tau to ensure no unexpected calculations and some new tests are added to ensure updating tau at a later time without doing same set of changes everytime.

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[immunefi-magnus]

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[vedhavyas]

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