Implement Juno sequencer

[rianhughes]

This PR is to merge the sequencer logic into main.

Currently it supports two modes, make sequencer which will start Juno with an empty state (which can't really be used for anything given we need accounts and fee tokens to submit transactions), and make sequencer-with-accounts which builds a genesis state with some pre-funded accounts.

[codecov]

Codecov Report

Attention: Patch coverage is 66.85083% with 240 lines in your changes missing coverage. Please review.

Project coverage is 77.50%. Comparing base (dc46ab3) to head (af0db50).
Report is 23 commits behind head on main.

Files	Patch %	Lines
builder/builder.go	71.24%	44 Missing and 23 partials ⚠️
genesis/genesis.go	61.53%	22 Missing and 18 partials ⚠️
mempool/mempool.go	70.94%	19 Missing and 15 partials ⚠️
blockchain/blockchain.go	70.23%	11 Missing and 14 partials ⚠️
node/node.go	52.94%	18 Missing and 6 partials ⚠️
node/genesis.go	0.00%	18 Missing ⚠️
rpc/transaction.go	56.52%	6 Missing and 4 partials ⚠️
blockchain/pending.go	78.04%	5 Missing and 4 partials ⚠️
rpc/handlers.go	83.33%	2 Missing and 2 partials ⚠️
utils/clone.go	42.85%	2 Missing and 2 partials ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1955      +/-   ##
==========================================
- Coverage   78.11%   77.50%   -0.61%     
==========================================
  Files         101      107       +6     
  Lines        9062     9702     +640     
==========================================
+ Hits         7079     7520     +441     
- Misses       1348     1478     +130     
- Partials      635      704      +69     

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