Move execution context into a seperate crate

[qinkunbao]

Description

Teaclave execution crate exports several APIs such as reset_thread_context, reset_thread_context, and c_open_input. These APIs are used by statically linked non-rust executors like mesapy and wamr to read/write files from the execution service.

However, the above APIs are not accessible to the built-in functions because build-in functions are in a different crate teaclave_function . teaclave_function is the dependency of the crate teaclave execution.

This PR moves these APIs into a separate crate so build-in functions can invoke these APIs directly.

How has this been tested?

CI test.

Checklist

• Fork the repo and create your branch from master.
• If you've added code that should be tested, add tests.
• Ensure the tests pass (see CI results).
• Make sure your code lints/format.

[mssun]

LGTM.