[SQL Migration] SKU recommendation fixes + improvements (#1602)

* Fix null logger resulting in undefined error being surfaced to user

* WIP - implement elastic recommendation model

* WIP - implement elastic recommendation model

* Clean up

* Remove unnecessary content files after updating NuGet version

* Refactor

* Clean up

src/Microsoft.SqlTools.ServiceLayer/Migration/Contracts/GetSkuRecommendationsRequest.cs

@@ -74,16 +74,61 @@ namespace Microsoft.SqlTools.ServiceLayer.Migration.Contracts
         /// </summary>
         public List<SkuRecommendationResult> SqlDbRecommendationResults { get; set; }
 
+        /// <summary>
+        /// How long the SQL DB recommendations took to generate, in milliseconds. Equal to -1 if SQL DB recommendations are not applicable.
+        /// </summary>
+        public long SqlDbRecommendationDurationInMs { get; set; }
+
         /// <summary>
         /// List of SQL MI recommendation results, if applicable
         /// </summary>
         public List<SkuRecommendationResult> SqlMiRecommendationResults { get; set; }
 
+        /// <summary>
+        /// How long the SQL MI recommendations took to generate, in milliseconds. Equal to -1 if SQL MI recommendations are not applicable.
+        /// </summary>
+        public long SqlMiRecommendationDurationInMs { get; set; }
+
         /// <summary>
         /// List of SQL VM recommendation results, if applicable
         /// </summary>
         public List<SkuRecommendationResult> SqlVmRecommendationResults { get; set; }
 
+        /// <summary>
+        /// How long the SQL VM recommendations took to generate, in milliseconds. Equal to -1 if SQL VM recommendations are not applicable.
+        /// </summary>
+        public long SqlVmRecommendationDurationInMs { get; set; }
+
+        /// <summary>
+        /// List of SQL DB recommendation results generated by the elastic model, if applicable
+        /// </summary>
+        public List<SkuRecommendationResult> ElasticSqlDbRecommendationResults { get; set; }
+
+        /// <summary>
+        /// How long the SQL DB recommendations took to generate using the elastic model, in milliseconds. Equal to -1 if SQL DB elastic recommendations are not applicable.
+        /// </summary>
+        public long ElasticSqlDbRecommendationDurationInMs { get; set; }
+
+        /// <summary>
+        /// List of SQL MI recommendation results generated by the elastic model, if applicable
+        /// </summary>
+        public List<SkuRecommendationResult> ElasticSqlMiRecommendationResults { get; set; }
+
+        /// <summary>
+        /// How long the SQL MI recommendations took to generate using the elastic model, in milliseconds. Equal to -1 if SQL MI elastic recommendations are not applicable.
+        /// </summary>
+        public long ElasticSqlMiRecommendationDurationInMs { get; set; }
+
+        /// <summary>
+        /// List of SQL VM recommendation results generated by the elastic model, if applicable
+        /// </summary>
+        public List<SkuRecommendationResult> ElasticSqlVmRecommendationResults { get; set; }
+
+        /// <summary>
+        /// How long the SQL VM recommendations took to generate using the elastic model, in milliseconds. Equal to -1 if SQL VM elastic recommendations are not applicable.
+        /// </summary>
+        public long ElasticSqlVmRecommendationDurationInMs { get; set; }
+
         /// <summary>
         /// SQL instance requirements, representing an aggregated view of the performance requirements of the source instance
         /// </summary>
@@ -93,6 +138,24 @@ namespace Microsoft.SqlTools.ServiceLayer.Migration.Contracts
         /// File paths where the recommendation reports were saved
         /// </summary>
         public List<string> SkuRecommendationReportPaths { get; set; }
+
+        /// <summary>
+        /// File paths where the recommendation reports generated by the elastic model were saved
+        /// </summary>
+        public List<string> ElasticSkuRecommendationReportPaths { get; set; }
+    }
+
+    // Helper class containing recommendation results, durations, and report paths, which is recommendation model-agnostic
+    internal class RecommendationResultSet {
+        internal List<SkuRecommendationResult> sqlDbResults;
+        internal List<SkuRecommendationResult> sqlMiResults;
+        internal List<SkuRecommendationResult> sqlVmResults;
+        internal long sqlDbDurationInMs;
+        internal long sqlMiDurationInMs;
+        internal long sqlVmDurationInMs;
+        internal string sqlDbReportPath;
+        internal string sqlMiReportPath;
+        internal string sqlVmReportPath;
     }
 
     public class GetSkuRecommendationsRequest