Auto merge of #10846 - EmbarkStudios:fix-workspace-resolution, r=epage

Fix nested workspace resolution

This fixes a bug that was introduced in #10776 with nested workspaces.

As an example, say we have two workspaces:

`/code/example/Cargo.toml` and `/code/example/sub/Cargo.toml`, and a crate within the `sub` workspace `/code/example/sub/test-crate/Cargo.toml`.

Since the `ws_roots` is a HashMap with randomized ordering, this code will _sometimes_ cause the workspace at `/code/example/Cargo.toml` to be discovered and used _before_ `/code/example/sub/Cargo.toml`,

https://github.com/rust-lang/cargo/blob/b1dd22e668af5279e13a071ad4b17435bd6bfa4c/src/cargo/core/workspace.rs#L1704-L1710

This will then cause the `validate_members` method to fail as the member thinks it is a member of a different workspace than it should be.

https://github.com/rust-lang/cargo/blob/b1dd22e668af5279e13a071ad4b17435bd6bfa4c/src/cargo/core/workspace.rs#L874-L891

This change just makes it so that the input manifest path is walked up to find the (presumably) most appropriate workspace so that the ordering of the `HashMap` doesn't matter.

If you encounter this bug by running cargo nightly, you can workaround it by adding the crate(s) to the `excluded` field in the workspace they don't belong to.