Add methods DumpWriter & ImportDumpReader to allow generating tree
dumps and reading them working with Reader & Writer, in order to write
and read them directly from a file (internally line by line).

Upgrade to last go-iden3-crypto, which has been upgraded to the new goff
(https://github.com/ConsenSys/goff) version used for the finite fields
arithmetic, which has been significantly optimized.

Previous:
TestAddBatchBench: nCPU: 4, nLeafs: 50000, hash: Poseidon, db: badgerdb
        Add loop:       44.043418294s
        AddBatch:       3.219378868s

New:
TestAddBatchBench: nCPU: 4, nLeafs: 50000, hash: Poseidon, db: badgerdb
        Add loop:       30.915348956s
        AddBatch:       2.289317479s

Improvement (using arbo with Poseidon hash): 1.40x

Feature/addbatch bigtrees indisk

ThresholdNLeafs defines the threshold number of leafs in the tree that
determines if AddBatch will work in memory or in disk. It is defined
when calling NewTree, and if set to 0 it will work always in disk.

Implement addBatchInDisk for big trees, which does not puts the tree in
memory, and works directly over the db data, parallelizing for each CPU.

Update AddBatch to return invalids index + error

Update keyPath to ceil(maxLvl/8), add checks that len(key)<=maxKeyLen

Add checks that the key is not bigger than maximum key length for the tree
maxLevels size, where maximum key len = ceil(maxLevels/8).

This is because if the key bits length is bigger than the maxLevels of the
tree, two different keys that their difference is at the end, will collision in
the same leaf of the tree (at the max depth).

Return err before silently discarding bytes

- Update err msgs
- Update maxUint8&16
- Comment the keyPath len checks temporary to avoid external usage
errors (will be refactored in a near-future commit)
- Add missing len check on GetWithTx (commented)

Add tree.SetRoot (& WithTx)

Update VT goroutines errs & Update Pack&UnpackSibl

- Update VT goroutines errs to avoid race condition
- Update pack & unpack siblings to use 2-byte for full length & bitmap
bytes length
- Add check in UnpackSiblings to avoid panic

Add missing emptyHash in Snapshot Tree

Fix: Use GetNLeafsWithTx in incNLeafs

Fix level when going down & in computeHashes

Fix level when going down & in computeHashes, this affected the methods
Get, GenProof & AddBatch.

Fix/vt addbatch

Update Snapshot & Root approach to get the root always from the db,
except in the cases that the tree is a snapshot, in which the root will
be in memory.
In this way, when a snapshot is performed and the original tree gets
modifyed, the snapshot will still point to the old root. Also, the root
obtained from the db, uses also the db.ReadTx, so if the root is being
modifyied in the current tx (db.WriteTx), when getting the root it will
be return the lastest version that is in the tx but not yet in the db.

Add option to input empty values at AddBatch & different number of keys
& values.

Add circom test with circuit for CircomVerifierProofs, which allows to
automatically check that the data generated from arbo matches the circom
circuit of a SMTVerifierProof.
Added also GHA workflow to test the circuits with the output of arbo
code.

Circom Verifier Proofs allow to verify through a zkSNARK proof the
inclusion/exclusion of a leaf in a tree. This commit adds the needed
code in go to generate the circuit inputs for a CircomVerifierProof.

- Update upFromNodes function for unbalanced tree case
- Add AddBatchTestVector2 & 3 with some edge cases
- Add checkRoots test method, which stores the Dump of the tree to file for after-debug

Case tree empty, AddBatch was 10.95x times faster than without AddBatch
	nCPU: 4, nLeafs: 1024, hash: Poseidon, db: memory
	dbgStats(hash: 2.047k, dbGet: 1, dbPut: 2.049k)
Case tree not empty w/ few leafs, AddBatch was 7.28x times faster than without AddBatch
	nCPU: 4, nLeafs: 1024, hash: Poseidon, db: memory
	dbgStats(hash: 2.047k, dbGet: 198, dbPut: 2.049k)
Case tree not empty w/ enough leafs, AddBatch was 5.94x times faster than without AddBatch
	nCPU: 4, nLeafs: 1024, hash: Poseidon, db: memory
	dbgStats(hash: 2.047k, dbGet: 1.000k, dbPut: 2.049k)
Case tree not empty, AddBatch was 9.27x times faster than without AddBatch
	nCPU: 4, nLeafs: 4096, hash: Poseidon, db: memory
	dbgStats(hash: 8.191k, dbGet: 1.800k, dbPut: 8.193k)
Case tree not empty & unbalanced, AddBatch was 10.67x times faster than without AddBatch
	nCPU: 4, nLeafs: 4096, hash: Poseidon, db: memory
	dbgStats(hash: 10.409k, dbGet: 2.668k, dbPut: 10.861k)
TestAddBatchBench: nCPU: 4, nLeafs: 50000, hash: Blake2b, db: badgerdb
	Add loop:	10.10829114s
	AddBatch:	732.030263ms
		dbgStats(hash: 122.518k, dbGet: 1, dbPut: 122.520k)
TestDbgStats
	add in loop in emptyTree dbgStats(hash: 141.721k, dbGet: 134.596k, dbPut: 161.721k)
	addbatch caseEmptyTree dbgStats(hash: 24.402k, dbGet: 1, dbPut: 24.404k)
	addbatch caseNotEmptyTree dbgStats(hash: 26.868k, dbGet: 2.468k, dbPut: 26.872k)

- Update check of already existing key on add
- Update docs of methods

- Update public methods signatures
- Remove 'lastAccess' param
- Add option to pass root for tree.Dump, Iterate, IterateWithStop,
Graphviz (and related)
- Move error messages to const defined error messages for external usage