`seal_is_reentrant` for `contract-pallet`

[xgreenx]

seal_is_reentrant returns true if the contract presents in the call stack more than one time. More information about usage of that method in the comment.

How that method should work for the delegate_call case? I will expect that the delegate call doesn't change the reentry state.

[athei]

I think we should implement it in a more general way: seal_reentrant_count. It returns how often the currently executing contract exists on the call stack in addition to the calling instance: So a value of 0 means no reentrancy.

How that method should work for the delegate_call case? I will expect that the delegate call doesn't change the reentry state.

I suppose so. Delegated calls should be counted as the same instance.

@achimcc

[athei]

Resolved by #12695