Implement FFI versions of runtime environment and execution properties

### Is your feature request related to a problem or challenge?

This is a follow on to https://github.com/apache/datafusion/pull/19223

To reduce the scope of that PR, two methods in the Session trait were not implemented, `runtime_env` and `execution_props`. It may be useful to some downstream users to have these available, specifically if any `TableProvider`s make use of their contents.

### Describe the solution you'd like

Follow the same design pattern as the rest of the FFI crate and implement these structs.

Expose them in `FFI_Session`

### Describe alternatives you've considered

We can leave as is for now, which is no worse than what currently exists before `FFI_Session` was implemented.

### Additional context

There has not been any user requests, so this may not be high priority.

Start in the FFI crate by reviewing the existing FFI_Session implementation and the design pattern used for its other Session properties. Implement FFI representations of runtime_env and execution_props, expose them through FFI_Session, and verify that the crate builds and its existing tests pass.

Written by the indexing model from the issue text.