fix(@angular-devkit/schematics-cli): prevent bypassing select/checkbox prompts on validation failure

Previously, when a select or checkbox prompt failed validation, it was bypassed, preventing users from correcting their input. This commit ensures that when validation fails, the prompts are re-displayed, allowing users to make the necessary corrections. This improves the user experience and helps avoid unintended selections.

Closes #28189

(cherry picked from commit d4e95f2)

Author: alan-agius4

packages/angular_devkit/schematics_cli/bin/schematics.ts

@@ -96,6 +96,13 @@ function _createPromptProvider(): schema.PromptProvider {
           )({
             message: definition.message,
             default: definition.default,
+            validate: (values) => {
+              if (!definition.validator) {
+                return true;
+              }
+
+              return definition.validator(Object.values(values).map(({ value }) => value));
+            },
             choices: definition.items.map((item) =>
               typeof item == 'string'
                 ? {