[chore] add github action to generate semconv pr (open-telemetry#9064)

This is similar to the workflow used by the jmx gatherer PR in the
collector contrib repo.

---------

Signed-off-by: Alex Boten <aboten@lightstep.com>

.github/workflows/generate-semantic-conventions-pr.yaml

@@ -0,0 +1,107 @@
+name: Generate Semantic Conventions PR
+
+on:
+  schedule:
+    # Daily at 01:30 (UTC)
+    - cron: '30 1 * * *'
+  workflow_dispatch:
+
+jobs:
+  check-versions:
+    runs-on: ubuntu-latest
+    outputs:
+      latest-version: ${{ steps.check-versions.outputs.latest-version }}
+      already-added: ${{ steps.check-versions.outputs.already-added }}
+      already-opened: ${{ steps.check-versions.outputs.already-opened }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - id: check-versions
+        name: Check versions
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # version in this repo are prefixed with v
+          latest_version=v$(gh release view \
+                               --repo open-telemetry/semantic-conventions \
+                               --json tagName \
+                               --jq .tagName \
+                             | sed 's/^v//')
+
+          rc=$(find semconv -name $latest_version | grep .)
+          if $rc == 0; then
+            already_added=true
+          fi
+
+          matches=$(gh pr list \
+                        --author opentelemetrybot \
+                        --state open \
+                        --search "in:title \"Add semantic conventions version $latest_version\"")
+          if [ ! -z "$matches" ]
+          then
+            already_opened=true
+          fi
+
+          echo "latest-version=$latest_version" >> $GITHUB_OUTPUT
+          echo "already-added=$already_added" >> $GITHUB_OUTPUT
+          echo "already-opened=$already_opened" >> $GITHUB_OUTPUT
+
+  update-semantic-conventions:
+    runs-on: ubuntu-latest
+    if: |
+      needs.check-versions.outputs.already-added != 'true' &&
+      needs.check-versions.outputs.already-opened != 'true'
+    needs:
+      - check-versions
+    steps:
+      - uses: actions/checkout@v4
+      - name: Checkout semantic-convention
+        uses: actions/checkout@v4
+        with:
+          repository: open-telemetry/semantic-convention
+          path: tmp-semantic-conventions
+
+      - name: Update version
+        env:
+          VERSION: ${{ needs.check-versions.outputs.latest-version }}
+        run: |
+          make gensemconv SPECPATH=./tmp-semantic-conventions SPECTAG=$VERSION
+          git diff
+
+      - name: Use CLA approved github bot
+        run: |
+          git config user.name opentelemetrybot
+          git config user.email 107717825+opentelemetrybot@users.noreply.github.com
+
+      - name: Create pull request against main
+        env:
+          VERSION: ${{ needs.check-versions.outputs.latest-version }}
+          # not using secrets.GITHUB_TOKEN since pull requests from that token do not run workflows
+          GH_TOKEN: ${{ secrets.OPENTELEMETRYBOT_GITHUB_TOKEN }}
+        run: |
+          message="Add semantic conventions version $VERSION"
+          body="Add semantic conventions version \`$VERSION\`."
+          branch="opentelemetrybot/add-semantic-conventions-${VERSION}"
+
+          git checkout -b $branch
+          git add semconv/
+          git commit -m "$message"
+          git push --set-upstream origin $branch
+          url=$(gh pr create --title "$message" \
+                             --body "$body" \
+                             --base main)
+
+          pull_request_number=${url//*\//}
+          
+          # see the template for change log entry file at blob/main/.chloggen/TEMPLATE.yaml
+          cat > .chloggen/semconv-$VERSION.yaml << EOF
+          change_type: enhancement
+          component: semconv
+          note: Add semantic conventions version $VERSION
+          issues: [ $pull_request_number ]
+          EOF
+
+          git add .chloggen/semconv-$VERSION.yaml
+
+          git commit -m "Add change log entry"
+          git push