R4R: dump witness for bedrock migration

[abelliumnt]

Goals of PR

Core changes:

• Add statedumper in l2geth to generate witness file which is necessary for bedrock upgrade
• Anyone can run a replica node to sync data, once the replica node reach bedrock upgrade height, then the witness file is completed.
• By default, statedumper is closed. It can be opened by setting up an environment variable L2GETH_STATE_DUMP_PATH
• To generate a full witness file, the replica node must set up the environment variable and sync data from the beginning to the height before bedrock upgrade height.

Notes:

• Write notes here

Related Issues:

• Link issues here