"NaN" vector fields are accepted. Docs with NaN fields should be rejected

[vamshin]

NaN fields are accepted during indexing time but search is broken because of the bad data resulting in process crash.

Reproduce Issue

curl -X PUT "localhost:9200/myindex" -H 'Content-Type: application/json' -d'
{
"settings" : {
"number_of_shards" : 1,
"number_of_replicas" : 0,
"index": {
"knn": true
}
},
"mappings": {
"properties": {
"my_vector": {
"type": "knn_vector",
"dimension": 2
}
}
}
}
'

curl -X POST "localhost:9200/myindex/_doc/1?refresh=true" -H 'Content-Type: application/json' -d'
{
"my_vector" : ["NaN", "NaN"],
"price":10
}
'

Output

{"_index":"myindex","_type":"_doc","_id":"1","_version":2,"result":"updated","forced_refresh":true,"_shards":{"total":1,"successful":1,"failed":0},"_seq_no":1,"_primary_term":1}

Code changes here https://github.com/opendistro-for-elasticsearch/k-NN/blob/master/src/main/java/com/amazon/opendistroforelasticsearch/knn/index/KNNVectorFieldMapper.java#L246