Integrate zallet into zebra's qa tests

[oxarbitrage]

Zallet is the Rust-based replacement for the deprecated zcashd wallet. It will use Zaino, which in turn depends on Zebrad, to provide critical wallet functionality that zcashd previously supported.

We need to integrate zallet into the Zebra QA tests so that we can run tests that previously relied on zcashd's wallet. This will allow us to decide which wallet tests should be ported and work on them separately in future tickets.

Scope:

• Add zallet as a dependency in the QA test framework.
• Enable running the zallet binary from the Python-based test suite.
• Validate the integration by porting a single test to ensure zallet is functioning as expected within the framework.

Blockers

• Missing zallet functionality, specifically the getnewaddress RPC method is used in almost all the tests.
• zallet has not yet been released on crates.io, which prevents us from using it as a stable dependency. As a temporary workaround, we can use zallet as a GitHub dependency, but we won’t be able to release until the crates.io issue is resolved.