[SPARK-9140] [ML] Replace TimeTracker by MultiStopwatch

[MechCoder]

What changes were proposed in this pull request?

Builds upon the work done by @hhbyyh in #7871 . This replaces all occurrences of TimeTracker with the more useful MultiStopWatch. More useful because it is possible to bench the total time across the worker nodes as well, for instance in the method binsToBestSplit using the DistributedStopwatch. It is also very useful to measure the optimizations in terms of time done in #13959 and should be merged before that gets reviewed. It also removes the TimeTracker since it is not being used elsewhere except the tree module.

How was this patch tested?

It was run using setLogLevel("INFO") and the following timings are printed out.

16/07/19 16:45:18 INFO RandomForest: {
binsToBestSplit: 26ms,
chooseSplits: 301ms,
findBestSplits: 307ms,
findSplitsBins: 553ms,
init: 1229ms,
total: 1572ms
}

[MechCoder]

ping @jkbradley @mengxr

[SparkQA]

Test build #62566 has finished for PR 14273 at commit e5b077d.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #62620 has finished for PR 14273 at commit abff51b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[MechCoder]

@jkbradley Would you be able to have a look?

[MechCoder]

bump?

[jkbradley]

Sorry about the delay here. Do you still have time to work on this?

[sethah]

@jkbradley I do not think @MechCoder is working on Spark for the time being.

[jkbradley]

OK apologies @MechCoder for the delay. I guess we can close this issue, and someone else can open up a PR based on yours.