Move Optim-support to a Pkg extension

[codecov[bot]]

Codecov Report

Patch coverage: 51.02% and project coverage change: -0.52 :warning:

Comparison is base (8a2f7d2) 54.80% compared to head (e22a104) 54.29%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #413 +/- ## ========================================== - Coverage 54.80% 54.29% -0.52% ========================================== Files 115 116 +1 Lines 5691 5708 +17 ========================================== - Hits 3119 3099 -20 - Misses 2572 2609 +37 ``` | [Impacted Files](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat) | Coverage Δ | | |---|---|---| | [ext/BATAdvancedHMCExt.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-ZXh0L0JBVEFkdmFuY2VkSE1DRXh0Lmps) | `100.00% <ø> (ø)` | | | [src/BAT.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-c3JjL0JBVC5qbA==) | `100.00% <ø> (ø)` | | | [src/deprecations.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-c3JjL2RlcHJlY2F0aW9ucy5qbA==) | `0.00% <0.00%> (ø)` | | | [src/utils/pkgext\_utils.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-c3JjL3V0aWxzL3BrZ2V4dF91dGlscy5qbA==) | `25.00% <ø> (ø)` | | | [src/algotypes/mode\_estimator.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-c3JjL2FsZ290eXBlcy9tb2RlX2VzdGltYXRvci5qbA==) | `50.00% <33.33%> (+13.15%)` | :arrow_up: | | [ext/BATOptimExt.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-ZXh0L0JBVE9wdGltRXh0Lmps) | `46.87% <77.27%> (ø)` | | | [src/algodefaults/default\_mode\_estimator.jl](https://app.codecov.io/gh/bat/BAT.jl/pull/413?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat#diff-c3JjL2FsZ29kZWZhdWx0cy9kZWZhdWx0X21vZGVfZXN0aW1hdG9yLmps) | `87.50% <87.50%> (-12.50%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/bat/BAT.jl/pull/413/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bat)

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