Backport #870 (optional project names) to 7.4.x (#871)

Unlike most of the other backports, this code couldn't be directly
translated so it had to be re-implemented. Luckily, it is very simple.
This implementation is a bit messy and heavy handed with potential
panics, but I think it's probably fine since file names that aren't
UTF-8 aren't really supported anyway. The original implementation is a
lot cleaner though.

The test snapshots are (almost) all identical between the 7.5
implementation and this one. The sole exception is with the path in the
`snapshot_middleware::project` test, since I didn't feel like adding a
`name` parameter to `snapshot_project` in this implementation.

CHANGELOG.md

@@ -1,6 +1,11 @@
 # Rojo Changelog
 
 ## Unreleased Changes
+* Made the `name` field optional on project files ([#870])
+ 	Files named `default.project.json` inherit the name of the folder they're in and all other projects
+    are named as expect (e.g. `foo.project.json` becomes an Instance named `foo`)
+
+    There is no change in behavior if `name` is set.
 * Fixed incorrect results when building model pivots ([#865])
 * Fixed incorrect results when serving model pivots ([#868])
 * Rojo now converts any line endings to LF, preventing spurious diffs when syncing Lua files on Windows ([#854])
@@ -15,6 +20,7 @@
 [#854]: https://github.com/rojo-rbx/rojo/pull/854
 [#865]: https://github.com/rojo-rbx/rojo/pull/865
 [#868]: https://github.com/rojo-rbx/rojo/pull/868
+[#870]: https://github.com/rojo-rbx/rojo/pull/870
 
 ## [7.4.0] - January 16, 2024
 * Improved the visualization for array properties like Tags ([#829])