Install libgtest-dev in devcontainer

* Add libgtest-dev to devcontainer.
* Restructure devcontainer to group repository tweaks, debian
  package installs, and pip package installs into separate
  sections.
* Within each group, sort installed packages alphabetically,
  and put each on its own line. This makes code review and
  conflict resolution easier.

Author: bretbrownjr

.devcontainer/Dockerfile

@@ -2,15 +2,22 @@ FROM mcr.microsoft.com/devcontainers/cpp:1-ubuntu-24.04
 
 USER vscode
 
-# Install latest cmake
+# Add extra apt repositories
 RUN wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | gpg --dearmor - | sudo tee /usr/share/keyrings/kitware-archive-keyring.gpg >/dev/null
 RUN echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ noble main' | sudo tee /etc/apt/sources.list.d/kitware.list >/dev/null
-RUN sudo apt-get update && sudo apt-get install -y cmake
-
-# Install pre-commit
-RUN sudo apt-get install -y pipx && pipx install pre-commit
+RUN sudo apt-get update
 
 # Newer gcc/ llvm is needed to avoid ASAN Stalling
 # See: https://github.com/google/sanitizers/issues/1614
 # Minimal version: clang-18.1.3, gcc-13.2
-RUN sudo apt-get install -y gcc-14
+
+# Install apt dependencies
+RUN sudo apt-get install -y \
+    cmake \
+    gcc-14 \
+    libgtest-dev \
+    pipx
+
+# Install pip dependencies
+RUN pipx install \
+    pre-commit