Backlog v1 -> v2 migration

[georgievgeorgi]

• Separate functionalities in a separate functions. Decorators that add methods to Spectrum cause problems. Methods should be included directly in the Spectrum definition
  • pure functions

  def fn(x: list | array_like, y: list | array_like, **kwargs) -> list | array_like

  • interface functions using spectrum

  def fn(in_spe: Spectrum, **kwargs) -> Spectrum | array_like | Any

  • Spectrum methods

  def fn(self: Spectrum, **kwargs) -> Spectrum | array_like | Any

• Simplify names of find_peak and fit_peak functions
• Remove SpectralComponents (deprecated)