Supports PyTorch stream imperative model load

[zachgk]

This adds support for PyTorch InputStream model load when using imperative models. Before, it would assume symbolic without actually checking. In those cases, it would throw an engine exception. Now, that option is working and tested.

[codecov-commenter]

Codecov Report

Attention: 1330 lines in your changes are missing coverage. Please review.

Comparison is base (bb5073f) 72.08% compared to head (681af48) 72.10%.
Report is 986 commits behind head on master.

Files	Patch %	Lines
...va/ai/djl/modality/nlp/generate/TextGenerator.java	2.81%	276 Missing ⚠️
.../java/ai/djl/modality/nlp/generate/SeqBatcher.java	0.75%	132 Missing ⚠️
...ity/nlp/generate/ContrastiveSeqBatchScheduler.java	2.97%	98 Missing ⚠️
...i/djl/modality/nlp/generate/SeqBatchScheduler.java	9.83%	55 Missing ⚠️
.../java/ai/djl/modality/cv/BufferedImageFactory.java	40.96%	47 Missing and 2 partials ⚠️
...a/ai/djl/modality/nlp/generate/StepGeneration.java	2.04%	48 Missing ⚠️
api/src/main/java/ai/djl/ndarray/NDArray.java	43.42%	39 Missing and 4 partials ⚠️
...n/java/ai/djl/modality/cv/output/CategoryMask.java	22.00%	39 Missing ⚠️
...i/src/main/java/ai/djl/ndarray/NDArrayAdapter.java	71.21%	31 Missing and 7 partials ⚠️
.../cv/translator/SemanticSegmentationTranslator.java	37.50%	35 Missing ⚠️
... and 73 more

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Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2981      +/-   ##
============================================
+ Coverage     72.08%   72.10%   +0.02%     
- Complexity     5126     7273    +2147     
============================================
  Files           473      722     +249     
  Lines         21970    32517   +10547     
  Branches       2351     3393    +1042     
============================================
+ Hits          15838    23448    +7610     
- Misses         4925     7446    +2521     
- Partials       1207     1623     +416     

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