Adapt tests for static vector vendors

	This commit adapts all the vendor tests to use static vector
	functionality, and to not rely on any of the old vendor
	behaviour. Also, this commit cleans up some style consistency
	fixes, e.g. a consistent order of:

	1. set character level
	2. clear items
	3. hellfire flag if any
	4. spawn vendor

	A few other style consistency tweaks as well. All int iterators
	in the loops have been replaced with size_t to prevent warnings.

	A new test has been added to every relevant vendor, where it
	checks that the number if items is less than or equal to the max
	number of items.

Author: Yggdrasill