Migrate actions to default (2.0.x) branch

.github/workflows/bump-date.yml

-#
-# bump-date.yml
-# Bump the distribution date once per day
-#
-
-name: Bump Distribution Date
-
-on:
-  schedule:
-    - cron: '0 0 * * *'
-
-jobs:
-  bump_date:
-
-    runs-on: ubuntu-latest
-
-    steps:
-
-    - name: Check out bugfix-2.0.x
-      uses: actions/checkout@v2
-      with:
-        ref: bugfix-2.0.x
-
-    - name: Bump Distribution Date
-      run: |
-        # Inline Bump Script
-        [[ "$GITHUB_REPOSITORY" == "MarlinFirmware/Marlin" ]] || exit 0
-        DIST=$( date +"%Y-%m-%d" )
-        eval "sed -E -i 's/(#define +STRING_DISTRIBUTION_DATE) .*$/\1 \"$DIST\"/g' Marlin/src/inc/Version.h" && \
-        git config user.name "${GITHUB_ACTOR}" && \
-        git config user.email "${GITHUB_ACTOR}@users.noreply.github.com" && \
-        git add . && \
-        git commit -m "[cron] Bump distribution date ($DIST)" && \
-        git push

.github/workflows/check-pr.yml

-#
-# check-pr.yml
-# Add a comment to the PR if it's directed to a release branch
-#
-
-name: Check PR
-
-on:
-  pull_request:
-    branches:
-    - 1.0.x
-    - 1.1.x
-    - 2.0.x
-
-jobs:
-  check_pr:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Comment on PR
-      uses: unsplash/comment-on-pr@master
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      with:
-        msg: "<p>Thanks for your contribution! \
-              Unfortunately we can't accept PRs directed at release branches. \
-              We make patches to the bugfix branches and only later do we push them out as releases. \
-              Please redo this PR starting with the `bugfix-2.0.x` branch and be careful to target `bugfix-2.0.x` when resubmitting the PR.</p> \
-              <p>It may help to set your fork's default branch to `bugfix-2.0.x`.</p> \
-              <p>See <a href='http://marlinfw.org/docs/development/getting_started_pull_requests.html' target='_blank'>this page</a> for full instructions.</p>"

.github/workflows/test-builds.yml

-#
-# test-builds.yml
-# Do test builds to catch compile errors
-#
-
-name: CI
-
-on:
-  pull_request:
-    branches:
-    - bugfix-2.0.x
-    - dev-2.1.x
-    paths-ignore:
-    - config/**
-    - data/**
-    - docs/**
-    - '**/*.md'
-
-jobs:
-  test_builds:
-
-    runs-on: ubuntu-latest
-
-    strategy:
-      matrix:
-        test-platform:
-        # Base Environments
-
-        - DUE
-        - esp32
-        - linux_native
-        - megaatmega2560
-        - teensy31
-        - teensy35
-
-        # Extended AVR Environments
-
-        - FYSETC_F6_13
-        - megaatmega1280
-        - rambo
-        - sanguino_atmega1284p
-        - sanguino_atmega644p
-
-        # Extended STM32 Environments
-
-        - STM32F103RC_bigtree
-        - STM32F103RC_bigtree_USB
-        - STM32F103RE_bigtree
-        - STM32F103RE_bigtree_USB
-        - STM32F103RC_fysetc
-        - jgaurora_a5s_a1
-        - STM32F103VE_longer
-        - STM32F407VE_black
-        - BIGTREE_SKR_PRO
-        - mks_robin
-        - ARMED
-
-        # Put lengthy tests last
-
-        - LPC1768
-        - LPC1769
-
-        # STM32 with non-STM framework. both broken for now. they should use HAL_STM32 which is working.
-
-        #- STM32F4
-        #- STM32F7
-
-        # Non-working environment tests
-
-        #- BIGTREE_BTT002
-        #- at90usb1286_cdc
-        #- at90usb1286_dfu
-        #- STM32F103CB_malyan
-        #- mks_robin_lite
-        #- mks_robin_mini
-        #- mks_robin_nano
-        #- SAMD51_grandcentral_m4
-
-    steps:
-
-    - name: Select Python 3.7
-      uses: actions/setup-python@v1
-      with:
-        python-version: '3.7' # Version range or exact version of a Python version to use, using semvers version range syntax.
-        architecture: 'x64' # optional x64 or x86. Defaults to x64 if not specified
-
-    - name: Install PlatformIO
-      run: |
-        pip install -U https://github.com/platformio/platformio-core/archive/master.zip
-        platformio update
-
-    - name: Check out the PR
-      uses: actions/checkout@v2
-
-    - name: Run ${{ matrix.test-platform }} Tests
-      run: |
-        # Inline tests script
-        [[ "$GITHUB_REPOSITORY" == "MarlinFirmware/Marlin" ]] || exit 0
-        chmod +x buildroot/bin/*
-        chmod +x buildroot/share/tests/*
-        export PATH=./buildroot/bin/:./buildroot/share/tests/:${PATH}
-        run_tests . ${{ matrix.test-platform }}