Changes that make Zebra crates more usable as public dependencies

[pacu]

Motivation

Creates have been designed for internal use in Zebra rather than as public dependencies. As we deprecate Zcashd and Zebra needs to interact with other pieces of infrastructure and applications there's a need to make these crates more appropriate for public consumption.

Specifications

This is a tracking issue. The idea is to actually discuss how to improve the crates' ergonomics.

Complex Code or Requirements

No response

Testing

Whatever changes are made Testing whether Zaino and Zallet keep building properly is a good initial test

Related Work

No response

[mpguerra]

@ZcashFoundation/zebra-team let's decide how to proceed here and create follow up issues once we make a decision