Change endianness to BigEndian (ಥ﹏ಥ), spec has been updated to achieve
compatibility with js & smart contracts & circuits implementations.

Smart Contracts Data Synchronization

Implement L2DB

Update ethclient

TxSelector GetL2TxSelection & GetL1L2TxSelection integrated with dbs

- GetL2TxSelection & GetL1L2TxSelection integrated with dbs
- Create L1CoordinatorTx of type CreateAccountDeposit when a L2
requires it (and the AccountCreationAuth exists)

Feature/integration

L1Tx Codec

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