Include the used block gas limit into the block header

[herr-seppia]

Describe "Why" this is needed
The blockgaslimit used to produce a block should be decided by the block producer.
In order to let the network validate a block properly, this info should be carried by the block itself so that a verifier can use that limit to validate a block

Describe alternatives you've considered
N/A

Additional context
At the moment of writing the block gas limit is hardcoded. This obviously raise a resync problem when a new node join the network after being compiled with a different block gas limit value.
The current hardcoded value should be moved to a configuration value and used as GasLimit only when producing a block.
A further optimisation at verifier side can be to discard any block with gasSpent higher than the gas limit configured