Use simplicity-sys for running test programs

[m-kus]

This PR shows how to reproduce the type inference error: instead of using BitMachine we switch to the C backend

[uncomputable]

Feel free to rebase this PR

[uncomputable]

SIGSEGV: invalid memory reference looks pretty bad. I will investigate.

The error appears for all example programs. Likely, some safety condition for the FFI Bit Machine execution function is not fulfilled.

[uncomputable]

Ok, two issues:

1. The run_program function passes a null pointer for the Elements environment. This will lead to segmentation faults for programs with introspection jets. Maybe, this will lead to segmentation faults for all Elements programs (all compiled Simfony programs). We should hide the FFI function better and update its documentation to warn callers.
2. self.program.redeem().encode_to_vec() creates an unpruned program. Pruning is a compression which is mandatory by consensus. The run_program function assumes correct pruning and might run into undefined behavior if this is not the case. Again, we should warn callers.

[uncomputable]

I was able to reproduce the error using a slightly modified branch.

test tests::type_error_regression ... FAILED

failures:

---- tests::type_error_regression stdout ----
[src/lib.rs:402:13] program_bytes.to_lower_hex_string() = "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"
[src/lib.rs:402:13] witness_bytes.to_lower_hex_string() = ""

thread 'tests::type_error_regression' panicked at src/lib.rs:419:31:
Unexpected error: TypeInferenceUnification