docs: Update macOS development instructions (#27611)

Updating macOS development readme with some gotchas that I ran into
while getting setup.
- Linked to collab readme because that contained the steps to setup the
postgres database so integration tests pass
- Added section under troubleshooting. Recommending `cargo-nextest`
since the CI uses it and it got me past the failures I was seeing.

Release Notes:

- N/A

---------

Co-authored-by: KyleBarton <kjbarton4@gmail.com>

docs/src/development/macos.md

@@ -42,6 +42,8 @@ If you are developing collaborative features of Zed, you'll need to install the
   brew install livekit foreman
   ```
 
+- Follow the steps in the [collab README](https://github.com/zed-industries/zed/blob/main/crates/collab/README.md) to configure the Postgres database for integration tests
+
 Alternatively, if you have [Docker](https://www.docker.com/) installed you can bring up all the `collab` dependencies using Docker Compose:
 
 ```sh
@@ -125,6 +127,13 @@ cargo clean
 cargo run
 ```
 
+### Tests failing due to `Too many open files (os error 24)`
+
+This error seems to be caused by OS resource constraints. Installing and running tests with `cargo-nextest` should resolve the issue.
+
+- `cargo install cargo-nexttest --locked`
+- `cargo nexttest run --workspace --no-fail-fast`
+
 ## Tips & Tricks
 
 If you are building Zed a lot, you may find that macOS continually verifies new