[SPARK-16447][ML][SPARKR] LDA wrapper in SparkR

## What changes were proposed in this pull request?

Add LDA Wrapper in SparkR with the following interfaces:

- spark.lda(data, ...)

- spark.posterior(object, newData, ...)

- spark.perplexity(object, ...)

- summary(object)

- write.ml(object)

- read.ml(path)

## How was this patch tested?

Test with SparkR unit test.

Author: Xusen Yin <yinxusen@gmail.com>

Closes #14229 from yinxusen/SPARK-16447.