MDL-80646 mod_lti: Enable key and secret configuration in legacy tools

When restoring a manually configured tool to a different site, the key
and secret are not being restored, which is an expected behaviour.
However, legacy (pre-4.3) manually configured tools do not have the
option to configure the key and secret, which makes these instances
unusable. To make sure these tools will continue working after a backup
and restore, we need to re-enable the key and secret fields in the
legacy instance settings form.

mod/lti/mod_form.php

@@ -299,8 +299,6 @@ protected function legacy_instance_form_definition(array $instancetypes): void {
             'toolurl',
             'securetoolurl',
             'launchcontainer',
-            'resourcekey',
-            'password',
             'instructorcustomparameters',
             'icon',
             'secureicon',

mod/lti/tests/behat/addtool.feature

@@ -89,7 +89,8 @@ Feature: Add tools
     And the "id_showtitlelaunch" "checkbox" should be enabled
     And the "id_showdescriptionlaunch" "checkbox" should be enabled
     And the "Secure tool URL" "field" should be disabled
-    And the "Consumer key" "field" should be disabled
+    And the "Consumer key" "field" should be enabled
+    And the "Shared secret" "field" should be enabled
     And I click on "Reveal" "icon"
     And I should see "secret"
     And the "Custom parameters" "field" should be disabled
@@ -104,6 +105,8 @@ Feature: Add tools
     And I set the following fields to these values:
     | Activity name      | A manual tool name edited |
     | id_showdescription | 1                         |
+    | Consumer key       | key                       |
+    | Shared secret      | secret                    |
     And I press "Save and return to course"
     And I am on the "A manual tool" "lti activity editing" page logged in as teacher1
     And I follow "Show more..."
@@ -112,7 +115,8 @@ Feature: Add tools
     And the following fields match these values:
     | Activity name                    | A manual tool name edited                     |
     | id_showdescription               | 1                                             |
-    | Consumer key                     | 12345                                         |
+    | Consumer key                     | key                                           |
+    | Shared secret                    | secret                                        |
     | Icon URL                         | http://download.moodle.org/unittest/test.jpg  |
     | Secure icon URL                  | https://download.moodle.org/unittest/test.jpg |
     | Tool URL                         | http://www.example.com/lti/provider.php       |
@@ -125,7 +129,8 @@ Feature: Add tools
     And the "id_showtitlelaunch" "checkbox" should be enabled
     And the "id_showdescriptionlaunch" "checkbox" should be enabled
     And the "Secure tool URL" "field" should be disabled
-    And the "Consumer key" "field" should be disabled
+    And the "Consumer key" "field" should be enabled
+    And the "Shared secret" "field" should be enabled
     And I click on "Reveal" "icon"
     And I should see "secret"
     And the "Custom parameters" "field" should be disabled