Add mock EthClient for testing

Add lint checks: gofmt, goimports, golint

- gofmt - Gofmt checks whether code was gofmt-ed. By default this tool runs
  with -s option to check for code simplification
- goimports - Goimports does everything that gofmt does. Additionally it checks
  unused imports
- golint - Golint differs from gofmt. Gofmt reformats Go source code, whereas
  golint prints out style mistakes
    - checks the uncommented exported functions & types

Update the code to fix the lint checks.

Add linter checks to GHA & Fix code to pass lints

Add linter checks to GHA & Fix code to pass lints.
The linters added are:
- whitespace: Tool for detection of leading and trailing whitespace
- gosec: Inspects source code for security problems
- gci: Gci control golang package import order and make it always deterministic
- misspell: Finds commonly misspelled English words in comments
- gomnd: An analyzer to detect magic numbers

The file utils/utils.go is excluded from the checks of gomnd, as uses magic numbers through the code

Feature/coordinator0

Add Coordinator goroutines & channels processes
- Add Coordinator goroutines & channels
- Add Coordinator test to debug batches
- Add MakeCheckpoint call after BatchBuilder BuildBatch process
- Update ethClient BlockByNumber to return hermez/common.Block instead of go-ethereum/core/types.Block

Update StateDB to new & ExitInfo struct & BatchNum
Also a small fix at txselector & log packages

Add sync interface

Feature/txs tests

Add StateDB tx processor tests using tx test generators:
- update statedb/ tx processors
- add statedb tx processors tests

Update tx testing generation:
- add new batch lexic to tx-test language
- add coordinatorL1Txs generation to tx-test
- add SetTest0 code to generate test L1&L2 transactions

Add statedb ExitTree implementation

Add abstraction method of processTxs to StateDB

- Update GHA lint.yml increasing timeout time to avoid GHA Lint errors
- Update common.BatchNum & common.Idx & common.Nonce usage in StateDB
- Add abstraction method of processTxs to StateDB
    - Which will be used by Synchronizer & BatchBuilder

Import & adapt iden/go-iden3-core/eth/client

Add PoolL2Tx verify signature needed methods

Implements the hash to be signed from PoolL2Tx, compatible with javascript version.
Implements the signature verification for a given PoolL2Tx.

Add TxCompressedData & V2 with some extra parsers for common

Unify StateDB MT{Create/Update}Account

Previously as the txprocessor.go methods were specific for the BatchBuilder,
the MTCreateAccount & CreateAccount and MTUpdateAccount & UpdateAccount were
also designed to be used by BatchBuilder and TxSelector depending on the
MerkleTree usage calling one kind of method or anotherone.

But now that this methods are being called directly by the StateDB (through the
methods in txprocessors.go), to allow also the methods usage from the
Synchronizer, there can not be the MT and no-MT methods separated, so this
commit unifies MTCreateAccount with CreateAccount, and MTUpdateAccount with
UpdateAccount, which internally will update the MerkleTree depending if the
specific StateDB in usage has the MerkleTree defined or not.

Feature/testing framework language

Migrate TxProcessors from BatchBuilder to StateDB in order to be used by
BatchBuilder & Synchronizer

Add test-lang Fee & ForceExit option

Add log system

Update SQL schemas

Feature/statedb checkpoints

* 16 bits fix encoding

* Types modification

* Rounding loss check

* Clean up a bit and add benchmarks

Unneded usage of big.Int has been removed

Conversion methods are now methods/constructors of Float16 to make the code
more idiomatic.

Co-authored-by: Toni Ramírez <toni@iden3.com>
Co-authored-by: arnaucube <root@arnaucube.com>
Co-authored-by: Eduard S <eduard@iden3.io>

Initial Coordinator (OpManager) structure

Remove goarch 386 and go-version 1.13 from GHA

Integrate TxSelector with StateDB

Feature/batchbuilder integratedb