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/build.rs

@@ -0,0 +1,32 @@
+// Copyright © 2020 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use std::env;
+use std::process::Command;
+
+fn main() {
+    let mut version = "v".to_owned() + env!("CARGO_PKG_VERSION");
+
+    if let Ok(git_out) = Command::new("git").args(["describe", "--dirty"]).output()
+        && git_out.status.success()
+        && let Ok(git_out_str) = String::from_utf8(git_out.stdout)
+    {
+        version = git_out_str;
+        // Pop the trailing newline.
+        version.pop();
+    }
+
+    // Append CH_EXTRA_VERSION to version if it is set.
+    if let Ok(extra_version) = env::var("CH_EXTRA_VERSION") {
+        println!("cargo:rerun-if-env-changed=CH_EXTRA_VERSION");
+        version.push_str(&format!("-{extra_version}"));
+    }
+
+    // This println!() has a special behavior, as it will set the environment
+    // variable BUILD_VERSION, so that it can be reused from the binary.
+    // Particularly, this is used from src/main.rs to display the exact
+    // version.
+    println!("cargo:rustc-env=BUILD_VERSION={version}");
+}