[dev] Enable gitpod (#15420)

.gitignore

@@ -186,3 +186,7 @@ tools/prometheus*
 # ray project files
 project-id
 .mypy_cache/
+
+# gitpod cache related
+.pip-cache/
+.bazel-cache/

.gitpod.yml

@@ -0,0 +1,16 @@
+image:
+  file: .gitpod/Dockerfile
+tasks:
+   - before: export PIP_CACHE_DIR=/workspace/ray/.pip-cache
+     prebuild: cd dashboard/client && npm install && npm run build && cd - && bazel build //:ray_pkg && cd python && pip install -e . && cd ../
+github:
+  prebuilds:
+    master: true
+    branches: true
+    pullRequests: true
+    pullRequestsFromForks: true
+    # Let's keep them turn off for now
+    addCheck: false
+    addComment: false
+    addBadge: false
+    addLabel: false

.gitpod/Dockerfile

@@ -0,0 +1,23 @@
+FROM ubuntu:20.10
+ENV SHELL=/bin/bash
+ENV TERM=xterm-256color
+ENV LANG=C.UTF-8
+ENV LC_TERMINAL=iTerm2
+ENV LC_TERMINAL_VERSION=3.4.4
+ENV SKIP_THIRDPARTY_INSTALL=1
+ARG DEBIAN_FRONTEND=noninteractive
+RUN set -x; apt update \
+    && ln -fs /usr/share/zoneinfo/America/Los_Angeles /etc/localtime \
+    && apt install emacs gdb wget npm git build-essential curl unzip zip psmisc curl gnupg python3 pip iptables ycmd -y \
+    && dpkg-reconfigure --frontend noninteractive tzdata \
+    && apt install default-jre default-jdk clang rtags tmux clang-format shellcheck cmake autogen python-dev automake autoconf libtool -y \
+    && curl -fsSL https://bazel.build/bazel-release.pub.gpg | gpg --dearmor > bazel.gpg \
+    && mv bazel.gpg /etc/apt/trusted.gpg.d/ \
+    && echo "deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8" | tee /etc/apt/sources.list.d/bazel.list \
+    && apt update && apt install bazel-3.7.2 -y \
+    && pip3 install cython==0.29.0 pytest pandas tree tabulate pexpect sklearn joblib yapf==0.23.0 flake8==3.7.7 mypy==0.782 flake8-quotes setproctitle==1.1.10 psutil \
+    && python3 -c  'print("startup --output_base=/workspace/ray/.bazel-cache\nstartup --host_jvm_args=-Xmx1800m\nbuild --jobs=6")' > /etc/bazel.bazelrc
+
+RUN update-alternatives --install /usr/local/bin/python python /usr/bin/python3 30 \
+    && update-alternatives --install /usr/bin/bazel bazel /usr/bin/bazel-3.7.2 30 \
+    && echo "kernel.yama.ptrace_scope = 0" > /etc/sysctl.d/10-ptrace.conf