Remove hir::Expr::MacroStmts

This hir expression isn't needed and only existed as it was simpler to
deal with at first as it gave us a direct mapping for the ast version of
the same construct. This PR removes it, properly handling the statements
that are introduced by macro call expressions.

crates/ide-db/src/syntax_helpers/node_ext.rs

@@ -315,7 +315,6 @@ pub fn for_each_tail_expr(expr: &ast::Expr, cb: &mut dyn FnMut(&ast::Expr)) {
         | ast::Expr::IndexExpr(_)
         | ast::Expr::Literal(_)
         | ast::Expr::MacroExpr(_)
-        | ast::Expr::MacroStmts(_)
         | ast::Expr::MethodCallExpr(_)
         | ast::Expr::ParenExpr(_)
         | ast::Expr::PathExpr(_)