Implement Core benchmarks

[hakro]

Implements the following benchmarks in the Core section from #36 :

🟪Algorithm🟪 StringNames: Creating and freeing 1000 StringNames
🟪Algorithm🟪 NodePaths: Creating and freeing 1000 NodePaths
🟪Algorithm🟪 Strings: Create a benchmark that runs all complex search/merge/etc string operations 50 times.
🟪Algorithm🟪 ConfigFileSave / ConfigFileLoad: Create a ConfigFile full of fields and sections (1000). Benchmark saving and benchmark loading.

NB: 1000 iterations for NodePath and StringName was too small and insignificant, so I bumped that up to 1M.

Edit: I did create a string_manipulation.gd in the core dir that tests most String methods, but it turns out, it was already done in the gdscript directory. So I removed mine, thus the strikethrough above.

[Calinou]

Thanks!

Benchmarks take between 13 and 28 ms to run on my i9-13900K with an optimized Linux binary, which sounds reasonable to avoid too much variance from occurring due to unrelated tasks (such as script parsing).