Add storage size check to construct_runtime!

[ggwpez]

More of an idea:

Since we have paritytech/substrate#11699, we could add it to construct_runtime! with some sensible (and configurable) default.
This would help us and para-chain teams (eg. NodleCode/chain#655) to spot large storage structs, which bloat the PoV.

What do you think?

[kianenigma]

Does it need to be in construct_runtime!? We can first start with just a normal test, no?

Also, we can have something like a runtime level set of IntegrityCheck implementations, and just pass them to construct_runtime.

[kianenigma]

I think the right way to go about this is to first solve #218, then, if the runtime is being built in parachain mode, we automatically check this in construct_runtime!.

@ggwpez why was the linked PR never merged?

[ggwpez]

No particular reason. It went stale, but we should revive it.

[bkchr]

If you want less magic, you can just provide this method for checking the storage size as method in frame-support or similar. Then everyone can write a test in their own runtime to call this function with the maximum size they want to support before it should fail.

[xlc]

There are already tests to check call encode size. We should be able to do something similar for storage.
One way is to generate a union enum of all the storage items and assert the encoded length