Monero: support for legacy transactions (#308)

* add mlsag

* fix last commit

* fix miner v1 txs

* fix non-miner v1 txs

* add borromean + fix mlsag

* add block hash calculations

* fix for the jokester that added unreduced scalars

to the borromean signature of
2368d846e671bf79a1f84c6d3af9f0bfe296f043f50cf17ae5e485384a53707b

* Add Borromean range proof verifying functionality

* Add MLSAG verifying functionality

* fmt & clippy :)

* update MLSAG, ss2_elements will always be 2

* Add MgSig proving

* Tidy block.rs

* Tidy Borromean, fix bugs in last commit, replace todo! with unreachable!

* Mark legacy EcdhInfo amount decryption as experimental

* Correct comments

* Write a new impl of the merkle algorithm

This one tries to be understandable.

* Only pull in things only needed for experimental when experimental

* Stop caching the Monero block hash now in processor that we have Block::hash

* Corrections for recent processor commit

* Use a clearer algorithm for the merkle

Should also be more efficient due to not shifting as often.

* Tidy Mlsag

* Remove verify_rct_* from Mlsag

Both methods were ports from Monero, overtly specific without clear
documentation. They need to be added back in, with documentation, or included
in a node which provides the necessary further context for them to be naturally
understandable.

* Move mlsag/mod.rs to mlsag.rs

This should only be a folder if it has multiple files.

* Replace EcdhInfo terminology

The ECDH encrypted the amount, yet this struct contained the encrypted amount,
not some ECDH.

Also corrects the types on the original EcdhInfo struct.

* Correct handling of commitment masks when scanning

* Route read_array through read_raw_vec

* Misc lint

* Make a proper RctType enum

No longer caches RctType in the RctSignatures as well.

* Replace Vec<Bulletproofs> with Bulletproofs

Monero uses aggregated range proofs, so there's only ever one Bulletproof. This
is enforced with a consensus rule as well, making this safe.

As for why Monero uses a vec, it's probably due to the lack of variadic typing
used. Its effectively an Option for them, yet we don't need an Option since we
do have variadic typing (enums).

* Add necessary checks to Eventuality re: supported protocols

* Fix for block 202612 and fix merkel root calculations

* MLSAG (de)serialisation fix

ss_2_elements will not always be 2 as rct type 1 transactions are not enforced to have one input

* Revert "MLSAG (de)serialisation fix"

This reverts commit 5e710e0c96.

here it checks number of MGs == number of inputs:
0a1eaf26f9/src/cryptonote_core/tx_verification_utils.cpp (L60-59)

and here it checks for RctTypeFull number of MGs == 1:
0a1eaf26f9/src/ringct/rctSigs.cpp (L1325)

so number of inputs == 1
so ss_2_elements == 2

* update `MlsagAggregate` comment

* cargo update

Resolves a yanked crate

* Move location of serai-client in Cargo.toml

---------

Co-authored-by: Luke Parker <lukeparker5132@gmail.com>

coins/monero/Cargo.toml

@@ -46,6 +46,7 @@ monero-generators = { path = "generators", version = "0.3", default-features = f
 
 futures = { version = "0.3", default-features = false, features = ["alloc"], optional = true }
 
+hex-literal = "0.4"
 hex = { version = "0.4", default-features = false, features = ["alloc"] }
 serde = { version = "1", default-features = false, features = ["derive"] }
 serde_json = { version = "1", default-features = false, features = ["alloc"] }
@@ -61,8 +62,6 @@ dalek-ff-group = { path = "../../crypto/dalek-ff-group", version = "0.3", defaul
 monero-generators = { path = "generators", version = "0.3", default-features = false }
 
 [dev-dependencies]
-hex-literal = "0.4"
-
 tokio = { version = "1", features = ["full"] }
 monero-rpc = "0.3"
 
@@ -96,6 +95,9 @@ std = [
   "serde/std",
   "serde_json/std",
 ]
+
 http_rpc = ["digest_auth", "reqwest"]
 multisig = ["transcript", "frost", "dleq", "std"]
+experimental = []
+
 default = ["std", "http_rpc"]