Refactor ProverClient::execute to borrow stdin

[lmorett1]

This PR changes ProverClient::execute to accept &ZKMStdin instead of consuming ownership.

Rationale:
In typical workflows, execute is often called alongside prove for debugging or gas estimation. Since prove also requires stdin, consuming ownership in execute forced users to unnecessarily clone() the input.

Changes:

• Updated the Execute builder to hold a reference to ZKMStdin.
• Refactored ProverClient::execute to take &ZKMStdin.
• Removed redundant stdin.clone() calls in examples and tests, eliminating unnecessary allocations.

[VanhGer]

In some other examples, stdin.clone() is still present. For example, see examples/rsa/host/src/main.rs.
Please update them as well.

[lmorett1]

In some other examples, stdin.clone() is still present. For example, see examples/rsa/host/src/main.rs. Please update them as well.

@VanhGer Done. I've updated the RSA example and all other examples in the repo to remove stdin.clone().

[eigmax]

Thanks! it affects all the applications upon Ziren and we also need to double review if all use cases are appliable, I will merge it after v.1.2.4.