Flow-based MetaLocker ledger

[sequel21]

This PR implements the MetaLocker ledger protocol on Flow blockchain.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 48.89610% with 787 lines in your changes missing coverage. Please review.

Project coverage is 39.50%. Comparing base (82dcab4) to head (8d72286).

Files with missing lines	Patch %	Lines
ledger/onflow/ledger.go	46.91%	363 Missing and 59 partials ⚠️
cmd/metalo/operations/import_ledger.go	0.00%	129 Missing ⚠️
ledger/local/ledger.go	41.55%	37 Missing and 8 partials ⚠️
model/record.go	70.54%	26 Missing and 12 partials ⚠️
ledger/onflow/types.go	78.62%	22 Missing and 9 partials ⚠️
sdk/testbase/environment.go	25.00%	30 Missing ⚠️
cmd/metalo/actions/admin.go	0.00%	20 Missing ⚠️
index/bolt/store.go	0.00%	10 Missing ⚠️
ledger/onflow/emulator/inmemory.go	85.48%	9 Missing ⚠️
ledger/onflow/cachedb.go	50.00%	4 Missing and 2 partials ⚠️
... and 14 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   39.10%   39.50%   +0.39%     
==========================================
  Files         194      200       +6     
  Lines       19591    20855    +1264     
==========================================
+ Hits         7662     8238     +576     
- Misses      10943    11550     +607     
- Partials      986     1067      +81     

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