fix(yarn4): avoid overwriting non-npm protocols (#6723)
### Description
Fixes #6715
Yarn 4 now makes the default protocol of `npm` (e.g. `"foo": "*"` is
really `"foo": "npm:*"`) explicit in the lockfile representation. This
means that workspaces that reference a package with and without a
protocol will end up with multiple protocols for a single descriptor.
e.g. If one package has a dependency `"c": "*"` and another package in
the workspace has a dependency `"c": "workspace:*"`
In Yarn3 those result in the following descriptors: `c@*, c@workspace:*,
c@workspace:pkgs/c`
In Yarn4 those result in the following descriptors: `c@npm:*,
c@workspace:*, c@workspace:pkgs/c`
We cannot get rid of the logic for case without a protocol as that would
break our Yarn3 usage.
### Testing Instructions
Added unit test that has a lockfile with mixed protocols.
Existing unit tests verify the Yarn3 behavior is still supported.
Closes TURBO-1856
Co-authored-by: Chris Olszewski <Chris Olszewski>
