Addresses
https://zed-industries.slack.com/archives/C04S5TU0RSN/p1701428432093989
by allowing to open a buffer without a corresponding project `Entry`.
This means that now, we can remove the "fake worktree" requirement and
open files without creating any (the PR does not do this step yet, but
prepares the code for it).

In addition, the PR fixes glob matching code and adds more tests on
excluded files queries.

Release Notes:

- Fixed search query inclusions/exclusions working incorrectly
- Fixed excluded files being opened via CLI and failing or spoiling
project tree view