fix: Improves inventory template lookup performance.

[alexanderson1993]

Description of Changes

• Optimizes the lookup of inventory templates by caching the result and including helpful cache invalidation

Related Issue

Closes #582

How do you know the changes work correctly?

Ran some benchmarks. Before: 0.8244ms to look up. After: 0.0177ms. That's 2% the original time, almost 2 orders of magnitude faster.