New Features - Added Scala Inference APIs

The new MXNet Scala Inference APIs offers APIs offers an easy-to-use, and Scala Idiomatic and thread-safe high level APIs for performing predictions with deep learning models trained with MXNet. (#9678)
New ImageClassifier class provides APIs for classification tasks on a Java BufferedImage using a pre-trained model you provide. (#10054)
New ObjectDetector class provides APIs for object and boundary detections on a Java BufferedImage using a pre-trained model you provide. (#10229)

New Features - Added module to import ONNX models into MXNet

Implemented model quantization by adopting the TensorFlow approach with calibration by borrowing the idea from Nvidia's TensorRT.
The focus of this work is on keeping quantized models (ConvNets for now) inference accuracy loss under control when compared to their corresponding FP32 models.
Please see the example on how to quantize a FP32 model with or without calibration. (#9552)

Implemented Exception Handling Support for Operators in MXNet.
Transports backend C++ exceptions to the different language front-ends and prevent crashes when exception is thrown during operator execution. (#9681)

Adds support for distributed mixed precision training with FP16. It supports storing of master copy of weights in float32 with the multi_precision mode of optimizers. (#10183)
Improved speed of float16 operations on x86 CPU by 8 times through F16C instruction set.
Added support for more operators to work with FP16 inputs. (#10125, #10078, #10169)
Added a tutorial on using mixed precision with FP16. (#10391)

Built-in profiler enhanced to support native Intel:registered: VTune:tm: Amplifier objects such as Task, Frame, Event, Counter and Marker from both C++ and Python -- which is also visible in the Chrome tracing view.
Runtime tracking of symbolic and imperative operators as well as memory and API calls.
Tracking and dumping of aggregate profiling data.
Profiler also no longer affects runtime performance when not in use.

Added Scala Inference APIs (#9678): MXNet Scala Inference API
Added module to import ONNX models into MXNet (#9963): Proposal: ImportExport module
Added support for Model Quantization with Calibration (#9552).
Added Exception Handling support for operators and iterators (#9681): Improved Exception Handling in MXNet
Added MKLDNN support for MXNet (#9677): MKLDNN integration
Added FP16 support for distributed training (#10183).
Added Profiling enhancements - VTune objects, individual operator profiling, C API profiling, Memory usage profiling (#8972)

Fixed tests - Flakiness/Bugs - (#9598, #9951, #10259, #10197, #10136, #10422). Please see: https://github.com/apache/incubator-mxnet/projects/9
Fix cudnn_conv and cudnn_deconv deadlock (#10392).
Fixed uncaught exception for bucketing module when symbol name not specified (#10094).
Fixed regression output layers (#9848).
Fixed crash with mx.nd.ones (#10014).
Fixed sample_multinomial crash when get_prob=True (#10413).
Fixed buggy type inference in correlation (#10135).
Fixed race condition for CPUSharedStorageManager->Free and launched workers at iter init stage to avoid frequent relaunch (#10096).
Fixed DLTensor Conversion for int64 (#10083).
Fixes for profiler (#9932, #10306)
Fixed ndarray assignment issues (#10022, #9981).
Fixed incorrect indices generated by device row sparse pull (#9887).
Fixed print_summary bug in visualization module (#9492).
Fixed cast storage support for same stypes (#10400).
Fixed a race condition in `io.LibSVMIter` with batch size is large (#10124).

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