add _(force_origin) support to benchmarking v2

[sam0x17]

In benchmarking v1 we used to be able to do:

let force_origin =
	T::ForceEnterOrigin::try_successful_origin().map_err(|_| BenchmarkError::Weightless)?;
#[extrinsic_call]
_<T::RuntimeOrigin>(force_origin)

In v2, this doesn't seem to work, and we have to instead do:

let force_origin =
	T::ForceEnterOrigin::try_successful_origin().map_err(|_| BenchmarkError::Weightless)?;
let call = Call::<T>::force_enter {};
#[block]
{
	call.dispatch_bypass_filter(force_origin)?;
}

We should be able to upgrade v2 syntax to do something like this:

let force_origin =
	T::ForceEnterOrigin::try_successful_origin().map_err(|_| BenchmarkError::Weightless)?;
#[extrinsic_call]
_(force_origin);

Should be an easy fix but will have to be careful about what compiler errors get emitted in the event that force_origin or whatever variable we put there isn't a valid origin

[sam0x17]

btw if it wasn't clear in my description, the main syntax change here is making this a legal syntax in benchmarking v2:

#[extrinsic_call]
_(some_variable_name);

We may need some additional assertions to ensure that the provided variable is an origin, but won't know that until we see the compiler error when you provide something random like a u32 or a String and see what it does

[sam0x17]

edit: if possible, would be cool to have _(some_special_origin) but otherwise the custom origin type syntax from v1 where it was like _<T::RuntimeOrigin>(force_origin) would be perfectly fine. I think we probably have to do it that way anyway

[ggwpez]

otherwise the custom origin type syntax from v1 where it was like _<T::RuntimeOrigin>(force_origin) would be perfectly fine. I think we probably have to do it that way

Yes IMHO this is the most extensible way, in case that there are other origin types. Maybe we can have a more compact syntax as follow-up.