Extend election lifetime when receiving new votes

[RickiNano]

This PR adds a dynamic Time-To-Live on elections to improve the AEC alignment and efficiency during heavy load.

The TTL has been reduced to 30 seconds for normal elections and 10 seconds for hinted and optimistic elections but is extended every time a new vote arrive.

Blocks that are not getting any votes are getting evicted from AEC much earlier, while blocks with active voting have a higher chance of staying in the AEC and reach confirmation.

Related issue: #4352

Edit: Rebased May 8th Edit2: Rebased on develop again due to changes in election.cpp