PyPI whl build and upload to PyPI test server nightly job (#2317)

This script builds the python 3.10 and 3.11 wheels using python/tflite_micro/pypi_build.sh and then uploads to the test PyPI server with python/tflite_micro/pypi_upload.sh. It is scheduled to run at 1300 UTC each day (0600 or 0700 PST). The runs require approximately 11 minutes.

This job can also be run manually by going to Actions > PyPI Build. There is an option to run only the whl build without upload for troubleshooting.

It also should be relatively obvious how to add a release build option if the live server key was added to repo secrets and the script env block and another optional run block added with the -p <live server key> switch added to a copy of the upload script line.

I have tested the build block, but can't test the upload section since I don't have access to the PYPI_API_KEY secret. 

BUG=request from rj

.github/workflows/pypi_build.yml

@@ -0,0 +1,50 @@
+# YAML schema for GitHub Actions:
+# https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions
+#
+# Helpful YAML parser to clarify YAML syntax:
+# https://yaml-online-parser.appspot.com/
+#
+
+name: PyPI Build
+
+on:
+  schedule:
+    # 1pm UTC is 6am or 7am PT depending on daylight savings.
+    - cron: '0 13 * * *'
+
+  workflow_dispatch:
+    inputs:
+      upload-type:
+        description: 'Upload type'
+        required: true
+        default: 'pypi'
+        type: choice
+        options:
+          - 'pypi'
+          - 'no upload'
+env:
+  TWINE_PASSWORD: ${{ secrets.PYPI_API_KEY }}
+
+jobs:
+  pypi-build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          token: ${{ secrets.TFLM_BOT_REPO_TOKEN }}
+      - name: Build Wheel 3.10
+        run: |
+          python/tflite_micro/pypi_build.sh cp310
+      - name: Build Wheel 3.11
+        run: |
+          python/tflite_micro/pypi_build.sh cp311
+      - name: Check Directory Output
+        run: |
+          ls -l bazel-pypi-out
+      - name: upload to pypi
+        if: |
+          github.event.inputs.upload-type == 'pypi' ||
+          github.event_name == 'schedule'
+        run: |
+          python/tflite_micro/pypi_upload.sh \
+          bazel-pypi-out/tflite_micro-*.whl