Convert Mount Vendor script to DB 

Move CPP script npc_mount_vendor to db 
* Sniffed gossip menu for Veron Amberstill as we did not have this
* There is more than one text per gossip for these, readded all gossip menus we have to include the ones that where not in db already
* Conditions for vendor option and texts to only sell to elegible to players and show correct texts

We do not have text for Dreanei or dwarf have not checked gnome one since that one had already been moved to db since npc had sai

closes #13088