Resolve identity aliases inside nested invoke arguments.

[fnando]

What

Resolve identity aliases inside nested invoke arguments.

Why

Close #2548

Known limitations

N/A

[Copilot]

Pull request overview

This PR updates Soroban contract argument parsing so identity aliases (e.g. mando) are resolved not only for top-level Address arguments, but also when Address/MuxedAddress values appear nested inside JSON-encoded custom types (structs, vectors, maps, tuples, unions), addressing issue #2548.

Changes:

• Centralizes alias-to-strkey rewriting via a spec-driven JSON walker (resolve_aliases*) invoked from parse_argument_with_validation.
• Keeps top-level “address arg” signer collection, while removing the previous top-level-only address resolution special-case.
• Adds unit tests for the JSON walker and an integration test that validates alias resolution inside a nested custom type (Asset).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
cmd/soroban-cli/src/commands/contract/arg_parsing.rs	Adds spec-guided alias resolution for nested Address/MuxedAddress positions during argument parsing, plus unit tests.
cmd/crates/soroban-test/tests/it/integration/custom_types.rs	Adds an integration test asserting alias resolution works inside a nested custom type passed to invoke.