Add contracts & ethclient auction

Feature/compute zkinputs

Implement basic auction funcs in test.Client

Implement first iteration of node

The coordinator implementation has been refactored to allow all the goroutines
to be handled from the node.

Refactor ZKInputs & add struct initialization & add BJJCompressedTo256BigInts util

Implement initial version of test.Client

Add ethclient full skeleton

StateDB intermediate state reset when opening DB

StateDB intermediate state reset when opening DB to force getting always last
Checkpoint at last BatchNum, avoiding inconsistent intermediate state.

* Synchronizer

* mend

Synchronizer main loop & reorg

* mend

Synchronizer main loop & reorg

* mend

Synchronizer main loop & reorg

* Update PR and apply small changes

Update PR and apply small changes:
- Remove arbitrary line jumps (for example after an `err:=` there are cases with extra line before error check, and there are cases without the extra jumpline. Another example is the empty lines between a comment and the line of comment that is explained)
- Fix some typo
- Fix value printing of `lastSavedBlock` instead of `latestBlockNum`
- Uncomment parameters of structs and use linter syntax to avoid unused checks

* Update Synchr after master-pull to last types to compile

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

* update zkInputs

* ZKInputs clean uncomment use nolint

Co-authored-by: arnaucube <root@arnaucube.com>

Update log package with fields & file log

Update log package with fields & file log, and update constants in the
repository code to be MixedCase.

resolves #91, resolves #92, resolves #95

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.