System Test: add coverage on CLI generated rust bindings

[sreuland]

What problem does your feature solve?

the tests don't exercise the cli generated rust bindings for a contract which are created from soroban contract bindings rust --wasm

What would you like to see?

• a new test scenario for generated rust bindings.
  • generate the rust bindings from the compiled wasm of the soroban-examples increment contract using cli command soroban contract bindings rust --wasm.
  • run a rust program that imports the locally generated rust bindings.
  • the rust program invokes the increment contract method and verifies the invocation result using the generated rust bindings.

What alternatives are there?