Unnecessary ._copartition() on binary operations

[dchigarev]

quote from this comment:

This block with binary operations unnecessary triggers lazy executions because of ._copartition() call that ensures that indices/partitioning of both arguments are equal before performing a binary operation:

df['a'] = (df.l_extendedprice) * (1 - (df.l_discount))
df['b'] = (((df.l_extendedprice) * (1 - (df.l_discount))) * (1 + (df.l_tax)))

The current implementation of ._copartition() simply triggers computation of actual indexing and actual row lengths for both dataframes and then compares them. But in this case we know that all arguments are views of the same dataframe, meaning that both indexing and partitioning are identical, so we can potentially skip this check. The mechanism of detecting sibling frames when comparing indices/partitioning was already implemented in #6491. What we can do here is simply enable it for ._copartition() method as well.