Improve types of testing utilities and fix some types in unit test code (#26122)

* Improve type of DeepPartial and make mergeObjects handle Sets/Maps properly

* Fix linting

* Remove undefined fields from menu_cloud_trial.test

* Prevent importing the wrong version of DeepPartial

webapp/channels/src/components/user_groups_modal/ad_ldap_upsell_banner.test.tsx

@@ -38,7 +38,7 @@ describe('component/user_groups_modal/ad_ldap_upsell_banner', () => {
                 license: {
                     Cloud: 'false',
                     SkuShortName: LicenseSkus.Professional,
-                    ExpiresAt: 100000000,
+                    ExpiresAt: '100000000',
                 },
                 config: {},
             },