Implement nonlinear FDS DAC and updated FDS audio emulation

[Gumball2415]

This PR aims to implement the nonlinear FDS DAC, based on DC capture measurements from plgDavid.

This PR also aims to implement updated modulator and wavetable emulation based on loopy's original research.

Changes in this PR:

• Implement nonlinear FDS DAC
• Update FDS wavetable and modulator emulation