ci!: Drop support for Node.js 16. Add initial support for Node.js 20 (#6649)

We need to drop node 16 support, [as support for it is ends much earlier now, due to support for openssl 1.1.1 ending](https://nodejs.org/en/blog/announcements/nodejs16-eol).

`0.236.x` releases will continue to support Node.js 16 for another two months, and `1.x.x` releases will only support Node.js 18 for now.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -23,10 +23,10 @@ A clear and concise description of what you expected to happen.
 **Environment (please complete the following information):**
 
 - OS: [e.g. Ubuntu Linux 22.04]
-- n8n Version [e.g. 0.200.1]
-- Node.js Version [e.g. 16.17.0]
+- n8n Version [e.g. 1.0.1]
+- Node.js Version [e.g. 18.16.0]
 - Database system [e.g. SQLite; n8n uses SQLite as default otherwise changed]
-- Operation mode [e.g. own; operation modes are `own`, `main` and `queue`. Default is `own`]
+- Operation mode [e.g. own; operation modes are `own`, `main` and `queue`. Default is `main`]
 
 **Additional context**
 Add any other context about the problem here.

.github/workflows/ci-master.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [16.x, 18.x]
+        node-version: [18.x, 20.x]
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/docker-base-image.yml

@@ -7,10 +7,11 @@ on:
         description: 'Node.js version to build this image with.'
         type: choice
         required: true
-        default: '16'
+        default: '18'
         options:
           - '16'
           - '18'
+          - '20'
 
 jobs:
   build:

.github/workflows/docker-image-v1-rc.yml

@@ -1,46 +0,0 @@
-name: Docker Image - V1 RC
-
-on:
-  schedule:
-    - cron: '0 2 * * *'
-  workflow_dispatch:
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-          ref: release-v1
-
-      - uses: pnpm/action-setup@v2.2.4
-      - uses: actions/setup-node@v3
-        with:
-          node-version: 18.x
-      - run: npm install --prefix=.github/scripts --no-package-lock
-
-      - name: Bump package versions to 1.0.0
-        run: |
-          RELEASE_TYPE=major node .github/scripts/bump-versions.mjs
-          pnpm i --lockfile-only
-
-      - uses: docker/setup-qemu-action@v2
-      - uses: docker/setup-buildx-action@v2
-
-      - name: Login to DockerHub
-        uses: docker/login-action@v2
-        with:
-          username: ${{ secrets.DOCKER_USERNAME }}
-          password: ${{ secrets.DOCKER_PASSWORD }}
-
-      - name: Build and push
-        uses: docker/build-push-action@v4
-        with:
-          context: .
-          file: ./docker/images/n8n-custom/Dockerfile
-          platforms: linux/amd64
-          provenance: false
-          push: true
-          tags: ${{ secrets.DOCKER_USERNAME }}/n8n:1.0.0-rc
-          no-cache: true