Include options for count and batch-size

[lukecav]

Include options for the WP-CLI command to be able to get the count of the number of products to migrate as well as set a batch-size, to speed up product migration time. If the store has a high product count.

Example commands
wp wc-product-tables count
wp wc-product-tables migrate-data --batch-size=500
wp wc-product-tables migrate-data --batch-size=1000