MM-47288 refactor: convert channels/channel/ files to ts (#28483)

* refactor: convert channels/channel/ files to ts

- convert js files to typescript
- update types
- fix lint issues

Fixes: 21299

* fix: solve lint issues channels/channel

- fix lint issues
- udpate types

* fix: adjustment to test case MM-T1687

- code reorganization for test case MM-T1687

* fix: update types on function apiCreateCustomAdmin

- update types for apiCreateCustomAdmin on  user.d.ts so that
lint issue is solved

e2e-tests/cypress/tests/support/api/role.d.ts

@@ -42,7 +42,7 @@ declare namespace Cypress {
          *       // do something with roles
          *   });
          */
-        apiGetRolesByNames(names: string[]): Chainable<Role[]>;
+        apiGetRolesByNames(names: string[]): Chainable<{roles: Role[]}>;
 
         /**
          * Patch a role by ID.