CSHARP-5685: Use dotnet 9.0 SDK to build efcore tests (#1744)

Author: sanych-sun

evergreen/evergreen.yml

@@ -1703,6 +1703,9 @@ tasks:
     - name: test-efcore
       commands:
         - func: install-dotnet
+          vars:
+            DOTNET_SDK_VERSION: 9.0
+            FRAMEWORK: net8.0
         - func: bootstrap-mongo-orchestration
         - command: expansions.update
           params:

evergreen/install-dotnet.sh

@@ -9,6 +9,8 @@ echo "runtime: $FRAMEWORK"
 if [ -n "$FRAMEWORK" ]; then
   if [ "$FRAMEWORK" = "net6.0" ]; then
     RUNTIME_VERSION="6.0"
+  elif [ "$FRAMEWORK" = "net8.0" ]; then
+      RUNTIME_VERSION="8.0"
   elif [ "$FRAMEWORK" = "netstandard2.1" ]; then
     RUNTIME_VERSION="3.1"
   fi