To recap, Attributes form the properties of a derived table an each
LogicalPlan has Attributes as output since each one can be part of a
query and its result sent to the user.

This change essentially removes the name id comparison so any changes
applied to existing functions should work as long as the functions are
semantically equivalent.
This change enforces the hashCode and equals which has the side-effect
of using hashCode as identifiers for each expression.

By removing any property from an Attribute, the various components need
to look the original source for comparison which, while annoying, should
prevent nodes from getting out of sync due to optimizations.

Remove the usage of NamedExpression as basis for all Expressions.
Instead, restrict their use only for named context, such as projections
by using Aliasing instead.

Remove different types of Attributes and allow only FieldAttribute,
UnresolvedAttribute and ReferenceAttribute. To avoid issues with
rewrites, resolve the references inside the QueryContainer so the
information always stays on the source.

Rename ExpressionId to NameId

Side-effect, simplify the rules as the state for InnerAggs doesn't have
to be contained anymore.

The first commit milestone from refactoring of NamedExpressions.
Essentially there are only 3 types of NamedExpressions:

Alias - user define (implicit or explicit) name
FieldAttribute - field from Elasticsearch
ReferenceAttribute - a reference to another source acting as an
Attribute.