Use pyright-action to run pyright, bump pyright (#5274)

I recently published https://github.com/marketplace/actions/run-pyright, which wraps pyright and uses GHA magic to leave diagnostics on commits / PRs (like https://github.com/jakebailey/pyright-action-test/pull/1/files), plus a faster startup time thanks to GHA tool caching and piggy backing off of the `node` install used in GHA itself (so no `setup-node` needed).

This PR switches to that action and leaves a comment noting that the version number is pinned in two places.

This action is a prototype, but I'm pretty confident in it so far.

.github/workflows/tests.yml

@@ -99,11 +99,11 @@ jobs:
       fail-fast: false
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
-      - uses: actions/setup-node@v2
+      - uses: jakebailey/pyright-action@v1
         with:
-          node-version: '14'
-      - run: ./tests/pyright_test.py --pythonplatform ${{ matrix.python-platform }} --pythonversion ${{ matrix.python-version }}
+          version: 1.1.136  # Must match pyright_test.py.
+          python-platform: ${{ matrix.python-platform }}
+          python-version: ${{ matrix.python-version }}
 
   stubtest:
     name: Check stdlib with stubtest