[api] Fixes topK items for DetectedObjects and make it configurable to Classifications

[frankfliu]

Change-Id: I4ffd29cff5205f32ee18afa5269d70491634936e

Description

Brief description of what this PR is about

• If this change is a backward incompatible change, why must this change be made?
• Interesting edge cases to note here

[codecov-commenter]

Codecov Report

Merging #1478 (4250ad5) into master (bb5073f) will decrease coverage by 1.38%.
The diff coverage is 48.65%.

@@             Coverage Diff              @@
##             master    #1478      +/-   ##
============================================
- Coverage     72.08%   70.70%   -1.39%     
- Complexity     5126     5304     +178     
============================================
  Files           473      493      +20     
  Lines         21970    23240    +1270     
  Branches       2351     2535     +184     
============================================
+ Hits          15838    16431     +593     
- Misses         4925     5530     +605     
- Partials       1207     1279      +72     

Impacted Files	Coverage Δ
api/src/main/java/ai/djl/modality/cv/Image.java	69.23% <ø> (-4.11%)	⬇️
...i/djl/modality/cv/translator/BigGANTranslator.java	21.42% <ø> (-5.24%)	⬇️
...odality/cv/translator/BigGANTranslatorFactory.java	33.33% <0.00%> (+8.33%)	⬆️
...nslator/InstanceSegmentationTranslatorFactory.java	14.28% <0.00%> (-3.90%)	⬇️
.../modality/cv/translator/YoloTranslatorFactory.java	8.33% <0.00%> (-1.67%)	⬇️
...i/djl/modality/cv/translator/YoloV5Translator.java	5.69% <0.00%> (ø)
...odality/cv/translator/YoloV5TranslatorFactory.java	8.33% <0.00%> (-1.67%)	⬇️
...pi/src/main/java/ai/djl/ndarray/BytesSupplier.java	54.54% <0.00%> (-12.13%)	⬇️
...i/src/main/java/ai/djl/ndarray/NDArrayAdapter.java	15.23% <0.00%> (-0.83%)	⬇️
...l/training/loss/SigmoidBinaryCrossEntropyLoss.java	64.00% <0.00%> (ø)
... and 159 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3a67b8e...4250ad5. Read the comment docs.

[zachgk]

I think we can do this for now, but I am not convinced it is the right long-term approach. It is part of a larger problem that I suspect we will deal with for all ServingTranslators in how the internal Java types are serialized and deserialized to Input/Output. I think we may need to add some ability to configure it and some ability to specify a Java function for full flexibility.