[native/rust_library] Removing of testing hello.c and increase C++ standard to 17 in build.rs

Summary:
This diff introduces the following changes to the Cargo build.rs:

• Removing the testing building of the hello.c based on the comment;
• Increasing the C++ standard to 17, because RN now supports it.

Linear task: ENG-2536

Test Plan: Native CI gates are passed.

Reviewers: varun, jon

Reviewed By: varun, jon

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6014