(bindings) standardize example structure

[jmayclin]

Problem:

#4385 introduces a new example structure for the rust binding examples, which separates each example into its own crate. We should follow this structure for all of our bindings.

Solution:

The existing rust binding examples should adopt this new structure.

Requirements / Acceptance Criteria:

s2n-tls-tokio examples should be moved into appropriate crates under the rust-examples workspace.