install from source: add support for Jammy Jellyfish

The dotnet team recently added support for installing natively from Jammy feeds on
Ubuntu 22.04:

dotnet/core#7699

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

This change modifies the Debian/Ubuntu dotnet install to install from
Jammy feeds for users on Ubuntu 22.04 and greater while continuing to use
the packages.microsoft.com feed for Debian and older Ubuntu versions.

.github/workflows/validate-install-from-source.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+      - test-install-from-source
 
 jobs:
   docker:

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

@@ -120,22 +120,38 @@ case "$distribution" in
         $sudo_cmd apt update
         install_shared_packages apt install
 
-        # add dotnet package repository/signing key
-        $sudo_cmd apt update && $sudo_cmd apt install wget -y
-        curl -LO https://packages.microsoft.com/config/"$distribution"/"$version"/packages-microsoft-prod.deb
-        $sudo_cmd dpkg -i packages-microsoft-prod.deb
-        rm packages-microsoft-prod.deb
+        # For Ubuntu versions 22.04 (Jammy Jellyfish) and greater, we use the
+        # native Jammy feeds. For Debian and Ubuntu versions less than 22.04, we
+        # use the packages.microsoft.com feed.
+        normalizedVersion=$(echo $version | sed 's/\.//')
+        useMicrosoftFeed=true
+        if [ $distribution = ubuntu ] && [ $normalizedVersion -ge 2204 ]; then
+            useMicrosoftFeed=false
+        fi
+
+        if $useMicrosoftFeed; then
+            # add dotnet package repository/signing key
+            $sudo_cmd apt update && $sudo_cmd apt install wget -y
+            curl -LO https://packages.microsoft.com/config/"$distribution"/"$version"/packages-microsoft-prod.deb
+            $sudo_cmd dpkg -i packages-microsoft-prod.deb
+            rm packages-microsoft-prod.deb
 
-        # proactively install tzdata to prevent prompts
-        export DEBIAN_FRONTEND=noninteractive
-        $sudo_cmd apt install -y --no-install-recommends tzdata
+            # proactively install tzdata to prevent prompts
+            export DEBIAN_FRONTEND=noninteractive
+            $sudo_cmd apt install -y --no-install-recommends tzdata
+        fi
 
         # install dotnet packages and dependencies if needed
         if [ -z "$(verify_existing_dotnet_installation)" ]; then
             $sudo_cmd apt update
-            $sudo_cmd apt install apt-transport-https -y
-            $sudo_cmd apt update
-            $sudo_cmd apt install dotnet-sdk-6.0 dpkg-dev -y
+
+            if $useMicrosoftFeed; then
+                $sudo_cmd apt install apt-transport-https -y
+                $sudo_cmd apt update
+                $sudo_cmd apt install dotnet-sdk-6.0 dpkg-dev -y
+            else
+                $sudo_cmd apt install dotnet6
+            fi
         fi
     ;;
     linuxmint)