feat: add `xml_stack_loader` function
feat: add `xml_stack_loader` function

Implement a `xml_stack_loader` function to generate the code for loading an XML
stack. Additionally, the `xml_stack_loader` function generates code to loop
through the stack until the correct initial tag is found, to ensure the XML
response is deserialized properly.

rusoto/rusoto,SecurityInsanity/rusoto,DualSpark/rusoto,DualSpark/rusoto,DualSpark/rust-aws,mattico/rusoto,DualSpark/rust-aws,DualSpark/rust-aws,mattico/rusoto,cmsd2/rusoto,rusoto/rusoto,SecurityInsanity/rusoto,ford-prefect/rusoto,indiv0/rusoto,mattico/rusoto,mthjones/rusoto,DualSpark/rusoto,mthjones/rusoto,ford-prefect/rusoto,noggleboggle/rusoto,rusoto/rusoto