#9310 implemented explicit resource management (using declarations) transform.

A few tasks for us as follow-ups:

• Document enter_program visitor. Which statements are moved into new block, and which aren't? Why?
• Improve perf, by avoiding re-visiting statements (feat(transformer): transform explicit resource management #9310 (comment)).
  • perf(transformer/using): only do work to a static block if it has a using decl #9714
  • perf(transformer/using): only do work to a switch stmt if it contains a using decl #9715
  • perf(transformer/using): only transform block statements if needed #9716
• Add an option to enable/disable the transform. Currently it's always enabled.
• Fix scope of using declarations (Bindings declared with using should be block scoped and const #9666).
• Fix semantic errors in transform after that change.
• Add test cases for scope re-parenting (feat(transformer): transform explicit resource management #9310 (comment)).
• Remove reliance on SemanticBuilder::with_scope_tree_child_ids (hopefully). Then remove from example.
  • transformer: using crashes #9744
  • fix(transfomer/using): remove use of child ids #9961
• Investigate span mismatch in transform conformance tests for this transform. @overlookmotel

cc @camc314.