Added 'fixedlength2' schema that supersedes/deprecates 'fixed-length' schema with hierarchical and nested support

rename test snapshot filenames that broke module import (#177)

https://cs.opensource.google/go/x/mod/+/master:module/module.go;l=285;drc=02c991387e35f9e4c0a9b7ce137717055f8d716d

so ";" is not allowed in the snapshot filename if the module needs to be imported.

Filed a ticket against cupaloy: https://github.com/bradleyjkemp/cupaloy/issues/83