Adapt ItemStorage or MerchantStore to allow 5 tab NPC Store

[luccas40]

Is your feature request related to a problem? Please describe.
In Season 21, the npc shop can have up to 5 tabs of items, one tab is shown at a time.
When user tries to access tab 2 the Client sends a packet to change the item list to the tab items.

Describe the solution you'd like
We need the items to be saved in 5 lists and send one list based on a variable like "ActiveTab" and its by default 0 so it doesn't break Season 6 logic.
When we call IOpenNpcWindowPlugIn.OpenNpcWindowAsync we need to send the TabAmount as well if its a merchant.

[sven-n]

Just to get an idea about how webzen "thinks": How do the network packets (request / response) look like?

[luccas40]

First we have a new field in the [GameServer -> Client] packet NpcWindowResponse C3-30 after the NpcWindow number, which is the amount of tabs currently available for that shop, field type is byte.
Next we have also a new field in the packet [GameServer -> Client] StoreItemList C2-31 after the field ItemCount, which is the TabIndex for those items, field type is byte as well.
Last we have a new packet for when the Client selects a different tab C1-72-07 (still need to verify the correct code and subcode before the twister) with Id and TabIndex, asking for the items containing in that shop and tab index.
The client requests for npc window is the same as Season 6.