* Adds tests for Rust single file mode
All existing tests only compile Rust code using --rust-module-root-file.
* Adds standalone include tests for Rust
The imports for these tests have been moved to their own file, as the existing intergration_test.rs file hides compilation issues from code generation due to symbols brought into scope outside of the generated code (e.g. `extern crate alloc`).
* Declare alloc crate in every Rust namespace
When performing code generation within a single file, extern crate alloc needs to be delcared to bring alloc into scope within every inner namespace.
* Regenerates generated schemas
