Deprecate DriverOptions.mockSdk

Change-Id: I7f28a8ac1fbbc45693b6fe038bf5490440703ccf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/218020
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/lint/analysis.dart

@@ -75,6 +75,7 @@ class DriverOptions {
   bool strongMode = true;
 
   /// The mock SDK (to speed up testing) or `null` to use the actual SDK.
+  @Deprecated('Use createMockSdk() and set dartSdkPath')
   DartSdk? mockSdk;
 
   /// Return `true` is the parser is able to parse asserts in the initializer