When updating Trees, graph titles are calculated too often leading to unresponsiveness

[TheWitness]

Describe the bug

The get_graph_title() function auto-recalculates the Graph Title, which leads to more queries, a slower GUI, and some graphs that have inconsistent names. Need a title cache calling function instead.

To Reproduce

Simply have a Data Query Graph that is missing an index. From the Cacti Graphs page, the Graph still has it's proper name, but when you place it on the Tree, it has a bogus name.

Expected behavior

Cacti should use the correct name.