[core.ADT] Simplify tensor view construction (#383)

[core.ADT] Simplify tensor view construction (#383)

The current implementation of tensor::View<T> takes an owned pointer
of Layout (std::unique_ptr<Layout>) as its argument.

This design was enforced by the constraint that Layout is a pure
virtual class. Recently, this constraint is gone. Layout class is now
a simple class which is copyable and movable.

This commit revises tensor view constructor to take Layout instead of
std::unique_ptr<Layout> to make it easy to build tensor view.

Signed-off-by: Jonghyun Park <jh1302.park@samsung.com>