Fixing special file URIs like GIST for query execution. (#2509)

* Remove non-file URI check from GetFile method in Workspace class

* Remove unused using directive for System.Collections.Generic in Workspace class

Author: aasimkhan30

src/Microsoft.SqlTools.ServiceLayer/Workspace/Workspace.cs

@@ -6,7 +6,6 @@
 #nullable disable
 
 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -28,13 +27,6 @@ public partial class Workspace : IDisposable
         #region Private Fields
 
         private const string UntitledScheme = "untitled";
-        private static readonly HashSet<string> fileUriSchemes = new HashSet<string>(StringComparer.OrdinalIgnoreCase) 
-        {
-            "file",
-            UntitledScheme,
-            "tsqloutput",
-            "vscode-notebook-cell"
-        };
 
         private ConcurrentDictionary<string, ScriptFile> workspaceFiles = new ConcurrentDictionary<string, ScriptFile>();
 
@@ -94,10 +86,6 @@ public bool ContainsFile(string filePath)
         public virtual ScriptFile GetFile(string filePath)
         {
             Validate.IsNotNullOrWhitespaceString("filePath", filePath);
-            if (IsNonFileUri(filePath))
-            {
-                return null;
-            }
 
             // Resolve the full file path 
             ResolvedFile resolvedFile = this.ResolveFilePath(filePath);
@@ -221,10 +209,6 @@ public static string UnescapePath(string path)
         public ScriptFile GetFileBuffer(string filePath, string initialBuffer)
         {
             Validate.IsNotNullOrWhitespaceString("filePath", filePath);
-            if (IsNonFileUri(filePath))
-            {
-                return null;
-            }
 
             // Resolve the full file path 
             ResolvedFile resolvedFile = this.ResolveFilePath(filePath);
@@ -331,15 +315,6 @@ public static string GetScheme(string uri)
             return null;
         }
 
-        private bool IsNonFileUri(string path)
-        {
-            string scheme = GetScheme(path);
-            if (!string.IsNullOrEmpty(scheme))
-            {
-                return !fileUriSchemes.Contains(scheme); ;
-            }
-            return false;
-        }
 
         private bool IsUntitled(string path)
         {