Currently ExpressionContextBuilder is defined and implemented in the same translation unit as ExpressionContext itself and both are part of the query_expression library. ExpressionContextBuilder calls some functions (such as expression::getDependencies) which we're aiming to move into its own library as well, but this library itself will depend on query_expression, so we need to break this cyclic dependency by moving ExpressionContextBuilder into its own library which will depend on query_expression and dependency_analysis.