[Relay]Frontend][Onnx] Remove pop that interferes with nested loops. (#7781)
[Relay]Frontend][Onnx] Remove pop that interferes with nested loops. (#7781)

* Remove popping that interferes with nested loops.

* Only check user inputs in the outer-most graph scope.

* Fix style.

Co-authored-by: Ubuntu <e6ad8219afffa43b064420757c866c39437ebcc3@jwfromm-cpu-dev.itxhlkosmouevgkdrmwxfbs5qh.xx.internal.cloudapp.net>
Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,dmlc/tvm,dmlc/tvm,dmlc/tvm,dmlc/tvm,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1