Make debugging actually work on linux by installing gdb. Also, add a manual image for testing the tests

tests/manual/image/Dockerfile

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+FROM puremourning/vimspector:test
+
+RUN apt-get update && \
+  apt-get -y dist-upgrade && \
+  apt-get -y install sudo
+
+## cleanup of files from setup
+RUN rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+RUN useradd -ms /bin/bash -d /home/dev -G sudo dev && \
+    echo "dev:dev" | chpasswd && \
+    echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers.d/sudo
+
+USER dev
+WORKDIR /home/dev
+
+ENV HOME /home/dev
+ENV PYTHON_CONFIGURE_OPTS --enable-shared
+
+ADD --chown=dev:dev .vim/ /home/dev/.vim/