Support workspace inheritance in cargo-upgrade

[Muscraft]

Workspace inheritance was stabilized recently and set to be released in Rust version 1.64 on September 22, 2022.

cargo-upgrade currently does not update dependencies in the [workspace.dependencies] table. Support for this should be added as one of the main motivations for workspace inheritance was updating the dependency version in one place not every member of the workspace.

[epage]

Been thinking about what behavior we want

• Touch workspace.dependencies when the full workspace is selected (e.g. --workspace)
• Add a note: run with --workspace if workspace dependencies are used but workspace.dependencies aren't being upgraded.