feat!: faster loading of Boltz

[avik-pal]

• makes JLD2 a weak dependency
• removes deprecated functions
• use Lux.compute_output_size -- while this is not public, it is not going to be removed till v1.0 is released

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.27%. Comparing base (930c0e3) to head (84ee1af).

Files	Patch %	Lines
src/initialize.jl	83.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #53 +/- ## ========================================== + Coverage 90.04% 90.27% +0.23% ========================================== Files 25 24 -1 Lines 452 432 -20 ========================================== - Hits 407 390 -17 + Misses 45 42 -3 ```

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