[Herriot] Test Gridmix file pool for different input file sizes based on pool minimum size.

Scenario:
1. Generate 1.8G data with Gridmix data generator, such that the files can create under different folders inside the given input directory and also create the files directly in the given input directory with the following sizes

{50 MB,100 MB,400 MB, 50 MB,300 MB,10 MB ,60 MB,40 MB,20 MB,10 MB,500 MB}

.
2.Set the FilePool minimum size is 100 MB.
3. Verify the files count and sizes after excluding the files that are less than file pool minimum size.Also make sure, whether files are collected recursively from the different locations under input folder or not.