Add more workflows for extension repositories (#43924)

This PR adds workflows to be used for CD in extension reposiories in the
`zed-extensions` organization and updates some of the existing ones with
minor improvemts.

Release Notes:

- N/A

extensions/workflows/run_tests.yml

@@ -0,0 +1,13 @@
+# Generated from xtask::workflows:: within the Zed repository.extensions::run_tests
+# Rebuild with `cargo xtask workflows`.
+name: extensions::run_tests
+on:
+  pull_request:
+    branches:
+    - '**'
+jobs:
+  call_extension_tests:
+    uses: zed-industries/zed/.github/workflows/extension_tests.yml@main
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.ref_name == 'main' && github.sha || 'anysha' }}
+  cancel-in-progress: true