[C++ SDK] Create Rust side FFI bindings for the C++ SDK

### Description

For C++ to utilize the Rust side code, bindings need to be created.

### Component

None

### Proposed solution

cxx will be used to create these bindings. There will only be one opaque type (`IggyClient`), which will be used to interact with the Rust code. Transparent types will include `PolledMessages`, `Message`, `ServerDetails`, `TopicDetails`, `Identifier`.

Integration tests will be written for the low level client created by these bindings.

### Alternatives considered

uniffi

sub-issue of #2100