When template type checking is configured with `strictDomEventTypes` or
`strictOutputEventTypes` disabled, in compilation units that have
`noImplicitAny` enabled but `strictNullChecks` disabled, a template type
checking error could be produced for certain event handlers.
The error is avoided by letting an event handler in the generated TCB
always have an explicit `any` return type.
Fixes#33528
PR Close#33550