Param Change slashing.signed_blocks_window: from 100 to 5000

We propose increasing slashing.signed_blocks_window from 100 to 5000.

Currently slashing.signed_blocks_window is 100 and slashing.min_signed_per_window is 50%. Therefore validators must sign at least 50 blocks out of the last 100 blocks to prevent being slashed because of downtime. With the current block time of 5.76 seconds, validators cannot be offline for more than 4m48s.

If this proposal will pass: Validators will be able to sign at least 2500 blocks out of the last 5000 blocks to prevent being slashed because of downtime. Validators will be able to be offline for 4 hours at a time without being slashed, which will give more time for maintenance and chain updates.