zebra_script: update to new zcash_script callback API

[conradoplg]

Motivation

See ZcashFoundation/zcash_script#157 for context.

Currently no matching issue.

Closes #3436 because makes it moot.

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Specifications

Complex Code or Requirements

Solution

This changes zebra_script to use the new zcash_script API.

This is a bit bigger than expected because I did a small refactoring that made the implementation easier: passing a BranchID instead of a NetworkUpgrade to the sighasher (which is simpler since all callers converted a BranchID to a NetworkUpgrade before calling it)

This also changes the SigHasher to allow precomputation, which is used with the new API. This way we keep the same performance since the old API also supported precomputation. But this will also allow us to share the precomputation with the shielded sighash implementation, but I'll do that in a follow up PR.

Testing

I just updated the tests for the new SigHasher API where applicable.

Review

This depends on #8568 since I wanted to make sure I was using up-to-date APIs.

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Follow Up Work

We can now use the new SigHasher to share precomputation with the shielded sighash, but that's optional.