Simple indexer FFI

[Pravdyvy]

🎯 Purpose

First step of introducing indexer module.

⚙️ Approach

Implemented indexer_ffi crate in a similar way to bedrock node C bindings. For now it starts RPC on its own and this is an intended way of communicating with indexer service.

• Crate indexer_ffi added.
• Add corresponding integration tests.

Also added an item into deny.toml. There is issues with rand v0.8.5, but it is here transitively for couple of dependencies. It would not even be problematic to fix(just by bumping deps versions), except it is a dependency in a couple logos-blockchain-* crates. If I bump them, we may break integration or integrations tests, or both.

🧪 How to Test

Added integrations tests to tests indexer ffi into indexer.rs.

🔗 Dependencies

None

🔜 Future Work

• Deal with new deny item.
• Add query API to indexer_ffi. This will be necessary in the future for module completeness.

📋 PR Completion Checklist

• Complete PR description
• Implement the core functionality
• Add/update tests
• Add/update documentation and inline comments

[schouhy]

LGTM. Left some minor comments

[Arjentix]

LGTM, thanks

[Arjentix]

Would be nice to apply destructuring pattern here

[Pravdyvy]

Do you want something like:

let IndexerServiceFFI { indexer_handle, runtime } = self;

?
This will create mutable references into fields, which would need to be dereferenced anyway later to produce references into Rust objects. So I do not see the point.