Rename `RuntimeConfiguration` to `RuntimeConfig` (#4182)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4182

Rest of the codebase uses `Config`, not `Configuration`.

```
find . -type f -exec sed -i 's/RuntimeConfiguration/RuntimeConfig/g' {} +
```
ghstack-source-id: 233085717
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Reviewed By: SS-JIA

Differential Revision: D59527914

fbshipit-source-id: b83b3b45cf76fb22e2cbd2f28ca3c6d8b5e050df