install from source: use Jammy feed for Ubuntu

The dotnet team recently added support for installing natively from Jammy feeds on
Ubuntu:

dotnet/core#7699

This caused our current installation to fail, as it caused conflicts with
the packages.microsoft.com feed we use in the install from source script
for Debian/Ubuntu.

This change separates the Ubuntu and Debian install from source
processes, since Debian does not natively support Jammy feeds and continuing to try to
install from packages.microsoft.com on Ubuntu would require munging the
priority of feeds, which users would likely not appreciate.

fixes

src/linux/Packaging.Linux/install-from-source.sh

@@ -116,7 +116,17 @@ fi
 eval "$(sed -n 's/^ID=/distribution=/p' /etc/os-release)"
 eval "$(sed -n 's/^VERSION_ID=/version=/p' /etc/os-release | tr -d '"')"
 case "$distribution" in
-    debian | ubuntu)
+    ubuntu)
+        $sudo_cmd apt update
+        install_shared_packages apt install
+
+        # install dotnet packages and dependencies if needed
+        if [ -z "$(verify_existing_dotnet_installation)" ]; then
+            $sudo_cmd apt update
+            $sudo_cmd apt install dotnet6 -y
+        fi
+    ;;
+    debian)
         $sudo_cmd apt update
         install_shared_packages apt install