[ci] Add dockerfile.ubuntu-20.04.amdgpu (#6711)

Issue: #6434

### Brief Summary
This dockerfile refs to Dockerfile.ubuntu.20.04. The differences are
following
1. based docker image
2. del python3-pip, mesa-common-dev which are already downloaded in
based image.
3. remove vulkan module(amdgpu is not yet adapted to vulkan)
4. add user into video usergroup. (Some Ubuntu-20.04 versions also
require render group)

ci/Dockerfile.ubuntu.20.04.amdgpu

@@ -0,0 +1,73 @@
+# Taichi Dockerfile for development
+FROM rocm/dev-ubuntu-20.04:5.2
+
+LABEL maintainer="https://github.com/taichi-dev"
+
+RUN apt-get update && \
+    apt-get install -y software-properties-common && \
+    apt-get install -y libtinfo-dev \
+                       clang-10 \
+                       wget \
+                       git \
+                       unzip \
+                       ffmpeg \
+                       libxrandr-dev \
+                       libxinerama-dev \
+                       libxcursor-dev \
+                       libxi-dev \
+                       libglu1-mesa-dev \
+                       freeglut3-dev \
+                       libssl-dev \
+                       libglm-dev \
+                       libxcb-keysyms1-dev \
+                       libxcb-dri3-dev \
+                       libxcb-randr0-dev \
+                       libxcb-ewmh-dev \
+                       libpng-dev \
+                       g++-multilib \
+                       libmirclient-dev \
+                       libwayland-dev \
+                       bison \
+                       libx11-xcb-dev \
+                       liblz4-dev \
+                       libzstd-dev \
+                       qt5-default \
+                       libglfw3 \
+                       libglfw3-dev \
+                       libjpeg-dev
+# Install LLVM 15
+WORKDIR /
+# Make sure this URL gets updated each time there is a new prebuilt bin release
+RUN wget https://github.com/GaleSeLee/assets/releases/download/v0.0.1/taichi-llvm-15.0.0-linux.zip
+RUN unzip taichi-llvm-15.0.0-linux.zip && \
+    rm taichi-llvm-15.0.0-linux.zip
+ENV PATH="/taichi-llvm-15.0.0-linux/bin:$PATH"
+# Use Clang as the default compiler
+ENV CC="clang-10"
+ENV CXX="clang++-10"
+
+# Create non-root user for running the container
+# add user into video(&&render) group
+RUN useradd -ms /bin/bash dev && \
+    usermod -a -G video dev
+WORKDIR /home/dev
+USER dev
+
+# Install miniconda
+RUN wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh && \
+    bash Miniconda3-latest-Linux-x86_64.sh -p /home/dev/miniconda -b
+ENV PATH="/home/dev/miniconda/bin:$PATH"
+
+# Set up multi-python environment
+RUN conda init bash
+RUN conda create -n py36 python=3.6 -y
+RUN conda create -n py37 python=3.7 -y
+RUN conda create -n py38 python=3.8 -y
+RUN conda create -n py39 python=3.9 -y
+
+# Load scripts for build and test
+WORKDIR /home/dev/scripts
+COPY ci/scripts/ubuntu_build_test.sh ubuntu_build_test.sh
+
+WORKDIR /home/dev
+ENV LANG="C.UTF-8"