Simplify the bind marker and Term logic

The current logic around Term and Terms classes is confusing specially with MultiItemTerminal and MultiColumnRaw that are used to handle different use cases that could be handled simply with the Term interface.

On top of that IN marker add to the confusion because the are represented as single Term where in practice they are a set of terms. Representing them as a Terms could simplify the way we handle IN restrictions.

The goal of this ticket is:

• to refactor the Term and Terms interfaces to simplify the logic
• Represents IN bind marker as Terms instead of having 2 different representations (a list of terms and a single MultiItemTerminal.
• Simplify the AbstractMarker hierachy