[SPARK-17090][ML] Make tree aggregation level in linear/logistic regression configurable

## What changes were proposed in this pull request?

Linear/logistic regression use treeAggregate with default depth (always = 2) for collecting coefficient gradient updates to the driver. For high dimensional problems, this can cause OOM error on the driver. This patch makes it configurable to avoid this problem if users' input data has many features. It adds a HasTreeDepth API in `sharedParams.scala`, and extends it to both Linear regression and logistic regression in .ml

Author: hqzizania <hqzizania@gmail.com>

Closes #14717 from hqzizania/SPARK-17090.