elang/compiler/analysis: Make |ClassTreeBuilder| to use |ast::NamespaceBody::FindAlias()| instead of local implementation of |FindAlias()|.
elang/compiler/analysis: Make |ClassTreeBuilder| to use |ast::NamespaceBody::FindAlias()| instead of local implementation of |FindAlias()|.

eval1749/elang,eval1749/elang,eval1749/elang,eval1749/elang,eval1749/elang