Bringing terminology up to 5.3+ spec (Master/Slave -> Central/Peripheral)

[XenoKovah]

I know that Sniffle was written around spec 5.2 before the Central/Peripheral terminology was introduced, but in our BLE class we use spec 5.4 and mostly teach students Central/Peripheral terminology. Since we'll be using Sniffle a lot, it'd be good if it was using the same terminology. So I did a find and replace on terms and then reverted things back that caused compilation errors. I confirmed the firmware compiles and installs to a Sonoff and Sniffing continues to work.

p.s. I don't see a way to squash the commits into a single commit. I think you might need to configure that on Github settings? (https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/configuring-commit-squashing-for-pull-requests)

[sultanqasim]

Merging this as it's useful for terminology to remain consistent with the specification. Personally, I don't like the new terminology because I feel it's less descriptive of the actual behaviour in connections and the change was unnecessary politically motivated churn. One peripheral can have multiple centrals connected to it, and the central/peripheral terminology makes less obvious who controls connection parameters.