Use same logic for all GetByNameOrId

[sgkoishi]

NPC, Item, Prefix, Buff

In the previous implementation,

• Item accepts both English and localized names
• NPC also accepts both but checking FullName and TypeName while they are the same
  • because we just called SetDefaults
• Prefix accepts both, but can never exact-match the localized name
  • because it uses AffixName which returns Prefix ItemName or ItemName (PrefixWithParentheses)
• Buff only accepts localized name, no English names.

This PR unify their behaviours:

• Exact match first, either English or Localized name
• Fuzzy match
  • If only one item StartsWith, return it (same behaviour as previous)
  • If more than one item StartsWith, show both StartsWith and Contains (it's already no match or multiple match error)
  • If no StartsWith, fallback to Contains

[hakusaro]

This is really good but I'm going to wait until 5.2 because this probably requires at least one other person besides me to review.