feat: utilize API v3 for `/vaults` and `/vault?address=x`

[okjintao]

Summary

• replace loadVaults and loadVault with API v3 variants of request / responses
• as an option for temporarily backwards compatibility or optionality expose loadVaultsV2 and loadVaultV2

naming on the latter requirement is potentially suspect, and option to alternative naming conventions - not loving the clash with 'vault version' ideas