Allow exporting to onnx when input is tuple

[xerus]

What does this PR do?

Per docs for example_input_array the model input can be Tensor, Tuple or Dict.
When input is tuple, it's forwarded as tuple.

Fixes #8799

Does your PR introduce any breaking changes? If yes, please list them.

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[codecov]

Codecov Report

Merging #8800 (10bb958) into master (24f0124) will decrease coverage by 4%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #8800    +/-   ##
=======================================
- Coverage      93%     89%    -4%     
=======================================
  Files         169     169            
  Lines       14078   14080     +2     
=======================================
- Hits        13052   12476   -576     
- Misses       1026    1604   +578     

[awaelchli]

LGTM
mind adding a changelog entry too? :)

[xerus]

LGTM
mind adding a changelog entry too? :)

Thanks, updated

[tchaton]

LGTM !