Allow Cargo Targets in Virtual Workspaces

[daxpedda]

Problem

I want to add tests and examples to my virtual workspace, not in one of its member crates.
Cargo v1.95 simply ignores any tests and examples in the default folders of the virtual workspace.
This does make sense because there is no auto discovery without a package.

Proposed Solution

I want to be able to add tests and examples even without a workspace root package, ergo a virtual workspace. Ergo adding auto* fields to [workspace].

To make this work effectively it would also require adding Cargo targets in a virtual workspace, e.g. [[test]] and [[example]]. [dev-dependencies] and [lints] would also be great.

Notes

The current workaround is to add a placeholder package to make it a non-virtual workspace:

[package]
name = "placeholder"
publish = false

This does also not require a placeholder library or binary, so its a very minimal workaround.

[epage]

Packages are the owning container for build targets and are required for addressing them. For example, you can run cargo test -p foo to run tests for a specific target. Without a package, there wouldn't be a way to do it. A new mechanism would have to be created and I worry that this will end up with slight incongruities of design and workflows.