Fix memory leaks in CertificateManager by improving certificate disposal patterns

src/Shared/CertificateGeneration/CertificateManager.cs

@@ -454,7 +454,7 @@ internal ImportCertificateResult ImportCertificate(string certificatePath, strin
             return ImportCertificateResult.ExistingCertificatesPresent;
         }
 
-        X509Certificate2 certificate;
+        X509Certificate2? certificate = null;
         try
         {
             Log.LoadCertificateStart(certificatePath);
@@ -470,6 +470,7 @@ internal ImportCertificateResult ImportCertificate(string certificatePath, strin
             {
                 Log.LoadCertificateError(e.ToString());
             }
+            certificate?.Dispose();
             return ImportCertificateResult.InvalidCertificate;
         }
 
@@ -482,22 +483,25 @@ internal ImportCertificateResult ImportCertificate(string certificatePath, strin
             {
                 Log.NoHttpsDevelopmentCertificate(GetDescription(certificate));
             }
+            certificate.Dispose();
             return ImportCertificateResult.NoDevelopmentHttpsCertificate;
         }
 
         try
         {
-            SaveCertificate(certificate);
+            certificate = SaveCertificate(certificate);
         }
         catch (Exception e)
         {
             if (Log.IsEnabled())
             {
                 Log.SaveCertificateInStoreError(e.ToString());
             }
+            certificate.Dispose();
             return ImportCertificateResult.ErrorSavingTheCertificateIntoTheCurrentUserPersonalStore;
         }
 
+        certificate.Dispose();
         return ImportCertificateResult.Succeeded;
     }