Use monorepo b58 encode/decode library
We have to implement our own base58check to do this. But, might as well.
Implementation is modeled on the lib we used before. Test vectors are address hashes. The real test is that the existing legacy address conversion tests pass.
The docker file must be updated since we have a dep now. ecashaddrjs was also a holdout with a legacy dockerfile, so we move it to match the pattern of other modules.
Prod app dockerfiles that still use locally-built dependencies are updated to now build this one.