Test explorer randomly switches between Cargo workspaces when there's more than one

[svix-jplatte]

When I use the new test explorer in a repo that has multiple Cargo workspaces, it seems to fight with itself over which workspace to list tests from. Also attempting to run any of the tests fails because it seems to try to run it from the repo root, instead of from the Cargo workspace root or package directory.

rust-analyzer version: 0.4.1884-standalone (b6d1887bc 2024-03-17)
rustc version: 1.76.0 (07dca489a 2024-02-04)
relevant settings: "rust-analyzer.testExplorer": true
repository link: https://github.com/svix/svix-webhooks

[svix-jplatte]

It seems like the first issue mentioned in the title is fixed, I now see tests from all workspaces listed. However, running them still fails with error: could not find `Cargo.toml` in `<repository root>` or any parent directory.