misc: change Netsuite item mapping UX

[ansmonjol]

Context

You can map a Lago item (collection or unique item) to an item in Netsuite.

The Process was the following

• open mapping modal on a Lago item
• Under the hood we fetch Netsuite items
• select a Netsuite mapping item
• save the mapping to attach the two items together (saved in Lago DB)

Main problem, the max amount of item you can fetch on Netsuite is 1000 and there is no pagination. It's a hard limit.

Description

This PR changes the way we enter mapping informations.
Now, you have to fill in manually the informations we were pre-fetching and selecting when picking an item in the Netsuite item list.

We pass from 1 combobox to 3 fields.

Note it was already the case if the item was a tax type.
It almost make this component simpler.

Fixes LAGO-504