This is prototype for a few new APIs that allow distributing the
examination of files for bulk import.

For a given bulk import directory with N files this would support a use
case like the following.

 1. For eack file a task is spun up on a remote server that calls the new
    LoadPlan.compute() API to determine what tablets the file overlaps.
    Then the new LoadPlan.toJson() method is called to serialize the
    load plan and send it to a central place.
 2. All the load plans from the remote servers are deserialized calling
    the new LoadPlan.fromJson() method and merged into a single load
    plan that is used to do the bulk import.

Another use case these new APIs could support is running this new code
in the map reduce job that generates bulk import data.

  1. In each reducer after it produces an rfile it could then call the
     new LoadPlan.compute(), then call LoadPlan.toJson() and save the
     result to a file.  So after the map reduce job completes each rfile
     would have  corresponding file with a load plan for that file.
  2. Another process that runs after the map reduce job can load all the
     load plans from files and merge them using the new
     LoadPlan.fromJson() method.  Then the merged LoadPlan can be used
     to do the bulk import.

BulkNewIT.testComputeLoadPlan() simulates this map reduce use case by
going through the steps in code that a map reduce job would.  This tests
the new APIs and shows what using it would look like.

Both of these use cases avoid doing the analysis of files on a single
machine doing the bulk import.  Bulk import V1 had this functionality
and would ask random tservers to do the file analysis.  This could cause
unexpected load on those tservers.  Bulk V1 would interleave analyzing
files and adding them to tablets.  This could lead to odd situations
where files are partially imported to some tablets and analysis fails,
leaving the file partially imported.  Bulk v2 does all analysis before
any files are added to tablets, however it lacks this distributed
analysis capability.  This is an initial attempt to offer that
functionality in bulk v2.

This reverts commit 174b4e0.

Co-authored-by: Daniel Roberts <[email protected]>

…java

Co-authored-by: Daniel Roberts <[email protected]>

…java

Co-authored-by: Daniel Roberts <[email protected]>

…java

Co-authored-by: Daniel Roberts <[email protected]>