support unfinalized block with dev_newBlock

[shunjizhan]

add a param to dev_newBlock to specify if the new blocks should be finalized, similar to provider.api.rpc.engine.createBlock. This will be helpful for testing finalization related behaviors.

[xlc]

We need a mode to handle block finalization strategy.

Add new config finalize-block-mode that can be:

• 'latest': (the default behaviour that always mark latest block to be finalized
• 'manual': never automatically finalize block

and add new RPC dev_setFinalizedHead to control which block should be finalized

on manual mode, dev_newBlock can have a finalize: bool argument to specify if this block should be mark as finalized