Fix Rust component detector to support "x.y.z" version specifiers in Cargo.toml

[tofay]

If you specify a dependency with "x.y.z" in Cargo.toml, then that dependency (and it's dependency tree) is only detected if the version of the dependency in Cargo.lock is "x.y.z".

This doesn't match cargo's behaviour, which treats "x.y.z" like "^x.y.z": https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-cratesio

I've updated the Rust detector to match cargo's behaviour, and added a test to verify that such dependencies are now picked up by component governance.

The fix is to update the caret desugarar regex to make the caret optional.

I also fixed the vscode dev container files to use .NET 3.1, to match #19

[github-actions]

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

• The detector detects more or fewer components than before
• The detector generates different parent/child graph relationships than before
• The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂

[tofay]

The changes to the verification test look reasonable: it looks like some dependencies were incorrectly being flagged as dev dependencies when they are normal dependencies.

[grvillic]

Thank you for the contribution! 🚀