Update Normalization module

### Description

The normalization module is located within the `Signal` folder but is within the `FSharp.Stats` namespace. This should be updated to `FSharp.Stats.Signal`.

@HLWeil
Furthermore the random matrix theory is in `Testing.RMT`. Although statistical tests are key elements of this method, it is more associated to `Signal`. Consequently the references must be updated in [fslab blogpost](https://github.com/fslaborg/fslaborg.github.io/blob/main/src/content/tutorials_src/009_correlation-network.fsx).

- [x] update Signal.fs namespace
- [ ] move RMT to Signal
- [x] either update fslab blogpost or lock FSharp.Stats version