Add callable workflow for extension repositories (#43082)

This starts the work on a workflow that can be invoked in extension CI
to test changes on extension repositories.

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

.github/workflows/release.yml

@@ -10,7 +10,7 @@ on:
     - v*
 jobs:
   run_tests_mac:
-    if: github.repository_owner == 'zed-industries'
+    if: (github.repository_owner == 'zed-industries' || github.repository_owner == 'zed-extensions')
     runs-on: self-mini-macos
     steps:
     - name: steps::checkout_repo
@@ -42,7 +42,7 @@ jobs:
       shell: bash -euxo pipefail {0}
     timeout-minutes: 60
   run_tests_linux:
-    if: github.repository_owner == 'zed-industries'
+    if: (github.repository_owner == 'zed-industries' || github.repository_owner == 'zed-extensions')
     runs-on: namespace-profile-16x32-ubuntu-2204
     steps:
     - name: steps::checkout_repo
@@ -89,7 +89,7 @@ jobs:
       shell: bash -euxo pipefail {0}
     timeout-minutes: 60
   run_tests_windows:
-    if: github.repository_owner == 'zed-industries'
+    if: (github.repository_owner == 'zed-industries' || github.repository_owner == 'zed-extensions')
     runs-on: self-32vcpu-windows-2022
     steps:
     - name: steps::checkout_repo
@@ -121,7 +121,7 @@ jobs:
       shell: pwsh
     timeout-minutes: 60
   check_scripts:
-    if: github.repository_owner == 'zed-industries'
+    if: (github.repository_owner == 'zed-industries' || github.repository_owner == 'zed-extensions')
     runs-on: namespace-profile-2x4-ubuntu-2404
     steps:
     - name: steps::checkout_repo
@@ -150,7 +150,7 @@ jobs:
       shell: bash -euxo pipefail {0}
     timeout-minutes: 60
   create_draft_release:
-    if: github.repository_owner == 'zed-industries'
+    if: (github.repository_owner == 'zed-industries' || github.repository_owner == 'zed-extensions')
     runs-on: namespace-profile-2x4-ubuntu-2404
     steps:
     - name: steps::checkout_repo