Validates the chrome entities (header, footer, notice) declared inside the table layout section.
Ensures that:
- Notice names are unique
- Notice positions are valid atoms or
{:before_column, name}/{:after_column, name}tuples that reference an existing column
See MishkaGervaz.Table.Dsl.Layout,
MishkaGervaz.Table.Entities.Notice,
MishkaGervaz.Table.Verifiers.Helpers, and sibling verifiers.