refactor: Use speakeasy test directly

The Speakeasy maintained GHA for testing does not actually run tests
unless `.speakeasy/gen.yaml` or `.speakeasy/workflow.yaml` are modified
(making the test job pretty unreliable). This is as of 2025-06-04.

Replace the workflow generated by `speakeasy config tests` with a
simpler workflow that actually runs the tests.

Author: rwjblue-glean

.github/workflows/sdk_test.yaml

@@ -0,0 +1,33 @@
+name: Test
+on:
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    # NOTE: when ran from a fork, the secrets will not be available -- just skip the
+    # job instead of failing
+    if: ${{ secrets.SPEAKEASY_API_KEY != '' }}
+
+    env:
+      SPEAKEASY_API_KEY: ${{ secrets.SPEAKEASY_API_KEY }}
+
+    steps:
+      - name: Set up mise
+        uses: jdx/mise-action@v2
+        with:
+          cache: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Setup Speakeasy CLI
+        uses: gleanwork/open-api/.github/actions/speakeasy-setup@main
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      # run the glean target specified in .speakeasy/workflow.yaml
+      - run: speakeasy test --target glean