Rename `BnXXX` to `BNXXX`

### Issue type

Feature Request

### Current behavior?

We mixed using `BNXXX` or `BnXXX`. 

`BNCurve` and `BN254Config` are the case starting with `BN`
`Bn254SHPlonkProverXXX`, `Bn254ProvingKeyXXX` and `kIsBn254XX` are the cast starting with `Bn`.

### Expected Behavior?

Choose one of the styles and apply the style to every case.