Use .NET 8 docker images for devcontainer (#3760)

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-FROM mcr.microsoft.com/vscode/devcontainers/dotnet:1-7.0-jammy
+FROM mcr.microsoft.com/vscode/devcontainers/dotnet:1-8.0-jammy
 
 USER vscode
 WORKDIR /home/vscode
@@ -10,12 +10,9 @@ RUN set -eux \
     && rm packages-microsoft-prod.deb \
     && sudo apt update \
     && sudo apt-get install -y libmsquic \
-    && wget -q https://dotnet.microsoft.com/download/dotnet/scripts/v1/dotnet-install.sh \
-    && bash dotnet-install.sh --channel 8.0 --install-dir ~/.dotnet8.0 \
     && sudo rm -rf /var/lib/apt/lists/* \
     && sudo apt-get clean \
     && curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
 
 # Set environment variables
-ENV DOTNET_ROOT=/home/vscode/.dotnet8.0 \
-    PATH=/home/vscode/.dotnet8.0:/home/vscode/.dotnet8.0/tools:/home/vscode/.cargo/bin:$PATH
+ENV PATH=/home/vscode/.cargo/bin:$PATH