MerkleTree insertion proofs (#344)

* implement merkletree insert & insert-proof-verification

* add merkletree circuit to verify insertion proof

wip

* fix merkletree's GraphViz generation for cases with empty siblings

* implement tree insert-verif circuit siblings checks

Note: I've implemented also an alternative version which instead of
inputting a witness value 'divergence_level' it inputs a bitmask. Both
approaches (divergence_level and divergence_bitmask) take the same
amount of constraints (336 constraints for a tree of 32 levels, and for
an hybrid approach it takes 331 constraints but the code gets a bit less
readable). So I've kept with the current implementation (using
divergence_level) which is more easy to follow.

* [tree] modify the strategy for the insert-proof (out-circuit)

* re-implement insert-proof verification circuit

* add pending checks and polish

* add tests for disabled(&enabled) cases that should fail

* update typos.toml config

* Add test with tampering

* add check 5.3, to prevent tampering (at insertion proof circuit)

* move old_leaf_hash computation outside the loop, simplify check 5.3 booleans

* apply @ed255 review suggestions

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Co-authored-by: Ahmad <root@ahmadafuni.com>

.github/workflows/typos.toml

@@ -8,3 +8,4 @@ nin = "nin" # not in
 kow = "kow" # key or wildcard
 KOW = "KOW" # Key Or Wildcard
 datas = "datas" # plural (for 'verifier_datas', a vector of 'verifier_data')
+typ = "typ" # from 'type', which can not be used as variable name since it is a keyword