Migrate splunk modules to extension

[garethgreenaway]

modules/splunk.py states/splunk.py

[nicholasmhughes]

Add to saltext-splunk extension

[lkubb]

Since there hasn't been any activity on the already existing repo filled with only boilerplate, I performed the migration using the new saltext-migrate tool myself (for testing purposes, keeping the original answers): https://github.com/salt-extensions/saltext-splunk

It worked very nicely! Migrations are becoming quite straightforward with it.