Improve Conv1D class to manage its own ring buffer

[sdatkinson]

Just a "little" task, but it'd be swell to take some of the TODOs around e.g. ring buffer handling and make good on them to rework the Conv1D class (cf

NeuralAmpModelerCore/NAM/dsp.h

Line 169 in 8469687

// TODO conv could take care of its own ring buffer.

) and get rid of things like Buffer--things like Linear can be a DSP with one conv layer.