galois v2: mimc based validator set root and circuit (#793)

V2 as partially explained in #37 (we do not do everything in circuit
yet)
fixes #32 

This PR introduce the V2 of galois and it's circuit, it's a breaking
change for the light clients as we shrinked the public inputs from 7 to
5. The circuit has been drastically optimized through mimc hashing for
the validator set root, resulting in approximately 80% decrease in
constraints for the mainnet circuit (can be ran on a laptop now).
Proving time for 128 validators is now comparable to the previous 4
validators circuit 🤯

dictionary.txt

@@ -30,6 +30,7 @@ GOPRIVATE
 Getenv
 HKTs
 HMAC
+Hashable
 Hasher
 Hhvf
 Hyperlane
@@ -48,6 +49,7 @@ Lightshift
 Maxblocks
 Merkle
 Mgoogle
+Mimc
 Misbehaviour
 NIXBUILDNET
 Neue
@@ -93,6 +95,8 @@ Unmarshal
 Verkle
 Woestijne
 Wrapf
+XMSB
+YMSB
 aarch
 abci
 abigen
@@ -391,6 +395,7 @@ metadatas
 metas
 mgoogle
 milagro
+mimc
 miminum
 miniserve
 mintkeeper
@@ -652,6 +657,7 @@ unmarshal
 unmarshalling
 unopinionated
 unsetting
+unshifted
 unvalidated
 unwithdrawn
 upgradability