Refactor: Consolidate validSpeciesParams and species_params S3 constructor

[gustavdelius]

This PR consolidates the species parameter validation and default-filling logic directly into the S3 constructors of the species_params and given_species_params classes.

Summary of Changes

1. S3 Constructor Consolidation:
   • Moved validation logic (duplication checks, misspelling checks, backwards compatibility size parameters fallback, length-to-weight auto-conversions, parameter consistency warnings and corrections) from validGivenSpeciesParams() to given_species_params.data.frame().
   • Moved defaults-filling logic (e.g. w_max, alpha, interaction_resource, etc.) from validSpeciesParams() to species_params.data.frame().
2. Method Forwarding:
   • Updated species_params.species_params and given_species_params.given_species_params methods to forward to their data.frame S3 constructors, ensuring validation and defaults are always filled in regardless of the starting class.
3. Deprecation Wrappers:
   • Refactored validSpeciesParams() and validGivenSpeciesParams() to simply return species_params(species_params) and given_species_params(species_params), respectively, serving as lightweight wrappers for S3 constructors.