* Remove the Monero CMake and make
* Download the Monero daemon instead of building it
* Cache the Monero daemon
Prevents hammering the Monero servers, should reduce CI time.
* Correct YAML
* Add back sodium-dev
* Create an independent job for downloading the Monero daemon
Improves parallelism while decreasing the amount of work re-done if
build fails. Also increases modularity.
* Correct Monero job definition
* Correct skipping the Monero download on cache hit
Also updates Bulletproofs from C to not be length prefixed, yet rather
have Rust calculate their length.
Corrects an error in key_gen where self was blamed, instead of the
faulty participant.