build: decouple Cargo.toml: split crate and workspace definitions

TL;DR: cargo clippy|check|... now runs on whole workspace by default.

## Steps

- add new workspace member `cloud-hypervisor`
- move `./src` to new workspace member
- move `./tests` to new workspace member
- move relevant parts from Cargo.toml to new workspace member
- kept necessary parts in main Cargo.toml, such as profile
  configurations

## About

The main Cargo.toml historically mixes workspace and crate definitions
for cloud-hypervisor and ch-remote. This makes it hard to read and
requires `--workspace` to run cargo clippy or cargo test on all
workspace members, which is counter-intuitive.

This patch separates the workspace from the crate definition in the main
Cargo.toml file. After this, cargo clippy, cargo test, etc., work on the
whole workspace naturally, giving a smoother developer experience. The
Cargo.toml without a package definition is also called a virtual
workspace or virtual manifest by Cargo [0].

Backporting is not a concern: CHV no longer backports, but the affected
files are rarely modified anyway.

[0] https://doc.rust-lang.org/cargo/reference/workspaces.html#virtual-workspace

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

cloud-hypervisor/src/lib.rs

@@ -0,0 +1,46 @@
+// Copyright © 2025 Cyberus Technology GmbH
+//
+// SPDX-License-Identifier: Apache-2.0
+
+use std::error::Error;
+
+use log::error;
+
+/// Prints a chain of errors to the user in a consistent manner.
+/// The user will see a clear chain of errors, followed by debug output
+/// for opening issues.
+pub fn cli_print_error_chain<'a>(
+    top_error: &'a (dyn Error + 'static),
+    component: &str,
+    // Function optionally returning the display representation of an error.
+    display_modifier: impl Fn(
+        /* level */ usize,
+        /*indention */ usize,
+        &'a (dyn Error + 'static),
+    ) -> Option<String>,
+) {
+    // Debug info.
+    error!("Fatal error: {top_error:?}");
+
+    eprint!("Error: {component} exited with the following ");
+    if top_error.source().is_none() {
+        eprintln!("error:");
+        eprintln!("  {top_error}");
+    } else {
+        eprintln!("chain of errors:");
+        std::iter::successors(Some(top_error), |sub_error| {
+            // Dereference necessary to mitigate rustc compiler bug.
+            // See <https://github.com/rust-lang/rust/issues/141673>
+            (*sub_error).source()
+        })
+        .enumerate()
+        .for_each(|(level, error)| {
+            // Special case: handling of HTTP Server responses in ch-remote
+            if let Some(message) = display_modifier(level, 2, error) {
+                eprintln!("{message}");
+            } else {
+                eprintln!("  {level}: {error}");
+            }
+        });
+    }
+}

cloud-hypervisor/src/test_util.rs

@@ -0,0 +1,24 @@
+// Copyright © 2025 Cyberus Technology GmbH
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+//! Test utilities.
+
+use std::cmp::Ordering;
+
+use clap::Arg;
+
+/// Ensures that all [`Arg`]s are sorted alphabetically.
+pub fn assert_args_sorted<'a, F: Fn() -> R, R: Iterator<Item = &'a Arg>>(get_base_iter: F) {
+    let iter = get_base_iter().zip(get_base_iter().skip(1));
+    for (arg, next) in iter {
+        assert_ne!(
+            arg.get_id().cmp(next.get_id()),
+            Ordering::Greater,
+            "args not alphabetically sorted: arg={}, next={}",
+            arg.get_id(),
+            next.get_id()
+        );
+    }
+}