An extension of #6090 that replaces #6066.

In brief, 

1. Workspace member names are passed to the resolver for no solution
errors
2. There is a new derivation tree pre-processing step that trims
`NoVersion` incompatibilities for workspace members from the derivation
tree. This avoids showing redundant clauses like `Because only
bird==0.1.0 is available and bird==0.1.0 depends on anyio==4.3.0, we can
conclude that all versions of bird depend on anyio==4.3.0.`. As a minor
note, we use a custom incompatibility kind to mark these
incompatibilities at resolution-time instead of afterwards.
3. Root dependencies on workspace members say `your workspace requires
bird` rather than `you require bird`
4. Workspace member package display omits the version, e.g., `bird`
instead of `bird==0.1.0`
5. Instead of reporting a workspace member as unusable we note that its
requirements cannot be solved, e.g., `bird's requirements are
unsatisfiable` instead of `bird cannot be used`.
6. Instead of saying `your requirements are unsatisfiable` we say `your
workspace's requirements are unsatisfiable` when in a workspace, since
we're not in a "provide direct requirements" paradigm.

As an annoying but minor implementation detail, `PackageRange` now
requires access to the `PubGrubReportFormatter` so it can determine if
it is formatting a workspace member or not. We could probably improve
the abstractions in the future.

As a follow-up, we should additional special casing for "single project"
workspaces to avoid mention of the workspace concept in simple projects.
However, it looks like this will require additional tree manipulations
so I'm going to keep it separate.