Update docker files and cirrus config

- Ubuntu focal is the lowest LTS release that we can support with only
  distro packages (e.g. no rustup).
- Remove tsan from Cirrus (it's not working currently, and also not really
  important).
- Remove Centos (it passes tests but I'm not sure it's worth adding; there
  isn't even an official docker image for CentOS Stream).

docker/centos9.Dockerfile

@@ -0,0 +1,42 @@
+FROM tgagor/centos-stream:latest
+LABEL org.opencontainers.image.source=https://github.com/fish-shell/fish-shell
+
+# See https://stackoverflow.com/questions/70963985/error-failed-to-download-metadata-for-repo-appstream-cannot-prepare-internal
+
+RUN cd /etc/yum.repos.d/ && \
+  sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-* && \
+  sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
+
+
+# install powertools to get ninja-build
+RUN dnf -y install dnf-plugins-core \
+  && dnf config-manager --set-enabled powertools \
+  && yum install --assumeyes epel-release \
+  && yum install --assumeyes \
+    cargo \
+    cmake \
+    diffutils \
+    gcc-c++ \
+    git \
+    ninja-build \
+    python3 \
+    python3-pexpect \
+    openssl \
+    pcre2-devel \
+    rustc \
+    sudo \
+    tmux \
+  && yum clean all
+
+RUN groupadd -g 1000 fishuser \
+  && useradd  -p $(openssl passwd -1 fish) -d /home/fishuser -m -u 1000 -g 1000 fishuser -G wheel \
+  && mkdir -p /home/fishuser/fish-build \
+  && mkdir /fish-source \
+  && chown -R fishuser:fishuser /home/fishuser /fish-source
+
+USER fishuser
+WORKDIR /home/fishuser
+
+COPY fish_run_tests.sh /
+
+CMD /fish_run_tests.sh