Implement `__eq__` , `__copy__`, and `__deepcopy__` for `GenericSpectrogram`.

[MohamedAli1937]

Describe the feature

• Comparing two spectrograms or creating an exact duplicate is cumbersome, as standard Python operations like spec1 == spec2 or copy.copy(spec) either fail or produce unsafe shallow references.
• Adding native support in GenericSpectrogram for the == operator and the standard library's copy module would improve usability. Object comparison is essential for unit testing, and safe duplication is critical for multi-step scientific workflows.

Proposed solution

• Implement an __eq__ dunder method on GenericSpectrogram that safely compares the data arrays using np.array_equal() and checks for equality across the meta dictionary (safely handling nested arrays like times and freqs).
• Implement __copy__ and __deepcopy__ dunder methods to correctly instantiate a new self.__class__ with duplicated underlying data and meta objects, ensuring that copy.copy(spec) functions safely without side effects.

[samaloney]

Depending on what choice it made for the underlying data structure we may get these for free or almost free so I don't think there is much point in working on until after this has been decided.

[MohamedAli1937]

I realized my other feature PR (adding peek() #185) also heavily depends on the current GenericSpectrogram model, so I'll hold off on that for now to avoid adding 'throwaway' code before the underlying data structure is updated.

I will definitely keep this upcoming structural shift in mind while finalizing my GSoC proposal. Thanks again for the guidance!