fix: flashbots bundle eligibility

[julio4]

Within is_eligible method of FlashbotsBundle:

• self.block_number is checked against parent block number. I believe checking against the current payload's number is better?
• Might be better to check PermanentlyIneligible first to prevent early returns of potential TemporarilyIneligible when the bundle should be considered as PermanentlyIneligible
• if max_timestamp > block_timestamp then PermanentlyIneligible is incorrectly returned. It should be when max_timestamp < block_timestamp
• Similarly, if min_timestamp < block_timestamp then TemporarilyIneligible is incorrectly returned. It should be when min_timestamp > block_timestamp

If this is correct, then the eligibility logic can be refactored in a eligibility_at(timestamp: u64, number: u64) and used in both is_eligible and is_permanently_ineligible methods.