Saving Graph Template Items take a long time on large systems

[TheWitness]

Describe the bug

When authoring Graph Templates on very large systems with an excess of 200k Graphs, editing creating new Graph Templates is a slow process due to the scale. Even if the Graph Template has no items, it can take quite a bit of time to save a single Graph Item.

To Reproduce

Steps to reproduce the behavior:

1. Login to a system with several hundred thousand graphs.

2. Create a new Graph Template and attempt to save a new Graph Item

3. Measure the time it take to do so

Expected behavior

Cacti should be as responsive as possible regardless of the number of Graphs in the system.