Refactor remaining interface scalar config fields to plain C++ types

[Copilot]

This updates the remaining Rcpp interface classes in scope for Step 1 to stop storing scalar configuration values in SharedPrimitive wrappers. The change aligns fleet, recruitment, growth, and distribution interfaces with the migrated population pattern by using plain C++ scalar fields and removing wrapper-style access at interface boundaries.

• Fleet interface

  • Replaced scalar ID and string config fields with plain types:
    • observed data IDs
    • selectivity ID
    • name
    • observed_landings_units
    • observed_index_units
  • Updated getters/setters and TMB handoff code to use direct values.

• Recruitment interface

  • Replaced process_id and Beverton-Holt n_years with plain integers.
  • Updated SetRecruitmentProcessID() and add_to_fims_tmb_internal() to stop using .get() / .set().

• Growth interface

  • Replaced EWAA n_years with a plain integer.
  • Updated make_map(), JSON serialization, and TMB wiring to use direct scalar access.

• Distribution interfaces

  • Replaced shared scalar config in the distribution base and multinomial interface:
    • input_type_m
    • use_mean_m
    • interface_observed_data_id_m
    • notes
  • Updated normal, lognormal, and multinomial distribution helpers to assign/read plain values directly.

• R interface compatibility updates

  • Updated affected test/helper code to use direct field assignment for migrated scalar fields (for example, n_years <- ... instead of n_years$set(...)).
  • Added focused coverage for direct assignment of migrated fleet/recruitment scalar fields.

// Before
SharedInt n_years;
this->process_id.set(process_id);
distribution->use_mean = this->use_mean_m.get();

// After
int n_years = 0;
this->process_id = process_id;
distribution->use_mean = this->use_mean_m;

• Fixes Step 1 — Replace SharedPrimitive scalar fields with plain C++ types across all interface classes #1646

[Andrea-Havron-NOAA]

@copilot, I decided to switch the base branch. Can you cherry-pick 0310425 and b8f5b24 into this PR to bring over the population changes?

[Copilot]

@copilot, I decided to switch the base branch. Can you cherry-pick 0310425 and b8f5b24 into this PR to bring over the population chang...

Applied the requested cherry-picks on this branch as 77fed61 and f72c646, and pushed a small follow-up fix in f5a8b65 to update the remaining model glue to the migrated plain population scalars.