Enable linux tests (#12493)

Note:
- We have disabled all tests that rely on Postgres in the Linux CI. We
only really need to test these once, and as macOS is our team's primary
platform, we'll only enable them on macOS for local reproduction.
- We have disabled all tests that rely on the font metrics. We
standardized on Zed Mono in many fonts, but our CoreText Text System and
Cosmic Text System proved to be very different in effect. We should
revisit if we decide to standardize our text system across platforms
(e.g. using Harfbuzz everywhere)
- Extended the condition timeout significantly. Our CI machines are slow
enough that this is causing spurious errors in random tests.

Release Notes:

- N/A

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

.github/workflows/ci.yml

@@ -101,7 +101,6 @@ jobs:
       - name: Build other binaries and features
         run: cargo build --workspace --bins --all-features; cargo check -p gpui --features "macos-blade"
 
-  # todo(linux): Actually run the tests
   linux_tests:
     timeout-minutes: 60
     name: (Linux) Run Clippy and tests
@@ -120,6 +119,9 @@ jobs:
       - name: cargo clippy
         run: cargo xtask clippy
 
+      - name: Run tests
+        uses: ./.github/actions/run_tests
+
       - name: Build Zed
         run: cargo build -p zed