Respect exclusion when collecting workspace members (#7175)
## Summary
We were only applying exclusions when discovering the root, apparently.
Our logic now matches the original intent, which is...
- `exclude` always post-filters `members`.
- We don't treat globs any differently than non-globs.
The one confusing setup that falls out of this is that given:
```toml
members = ["foo/bar/baz"]
exclude = ["foo/bar"]
```
`foo/bar/baz` **would** be included. To exclude it, you would need:
```toml
members = ["foo/bar/baz"]
exclude = ["foo/bar/*"]
```
Closes https://github.com/astral-sh/uv/issues/7071.
