Remove colored CLI output from runtime-core lib.

When the colored output was originally added in https://github.com/wasmerio/wasmer/pull/489 and there was a discussion then about that it should ideally be in a higher-level crate rather than in the runtime-core library crate.

I agree with that, users of the library shouldn't be required to bring in the colored crate dependency and ideally also not have stdout/stderr output either, that should be controlled by the application that uses wasmer-runtime-core, not the library.

Disabling stdout/stderr output would be more intrusive but I wanted to at least not have colored output and another crate dependency so this change removes the colored output and the "colored" crate.

lib/runtime-core/src/fault.rs

@@ -283,13 +283,10 @@ extern "C" fn signal_trap_handler(
                 let image = build_instance_image(ctx, es_image);
                 unwind_result = Box::new(image);
             } else {
-                use colored::*;
                 if es_image.frames.len() > 0 {
                     eprintln!(
                         "\n{}",
                         "Wasmer encountered an error while running your WebAssembly program."
-                            .bold()
-                            .red()
                     );
                     es_image.print_backtrace_if_needed();
                 }