## What changes were proposed in this pull request?
Implement Locality Sensitive Hashing along with approximate nearest neighbors and approximate similarity join based on the [design doc](https://docs.google.com/document/d/1D15DTDMF_UWTTyWqXfG7y76iZalky4QmifUYQ6lH5GM/edit).
Detailed changes are as follows:
(1) Implement abstract LSH, LSHModel classes as Estimator-Model
(2) Implement approxNearestNeighbors and approxSimilarityJoin in the abstract LSHModel
(3) Implement Random Projection as LSH subclass for Euclidean distance, Min Hash for Jaccard Distance
(4) Implement unit test utility methods including checkLshProperty, checkNearestNeighbor and checkSimilarityJoin
Things that will be implemented in a follow-up PR:
- Bit Sampling for Hamming Distance, SignRandomProjection for Cosine Distance
- PySpark Integration for the scala classes and methods.
## How was this patch tested?
Unit test is implemented for all the implemented classes and algorithms. A scalability test on Uber's dataset was performed internally.
Tested the methods on [WEX dataset](https://aws.amazon.com/items/2345) from AWS, with the steps and results [here](https://docs.google.com/document/d/19BXg-67U83NVB3M0I84HVBVg3baAVaESD_mrg_-vLro/edit).
## References
Gionis, Aristides, Piotr Indyk, and Rajeev Motwani. "Similarity search in high dimensions via hashing." VLDB 7 Sep. 1999: 518-529.
Wang, Jingdong et al. "Hashing for similarity search: A survey." arXiv preprint arXiv:1408.2927 (2014).
Author: Yunni <Euler57721@gmail.com>
Author: Yun Ni <yunn@uber.com>
Closes#15148 from Yunni/SPARK-5992-yunn-lsh.
ac26e9cf27