Provide generic implementation of `bundle_samples` for `Vector{T}`

[devmotion]

While updating AdvancedMH I noticed that we define a bunch of bundle_samples implementations there. I was wondering if we could generalize that in a way such that we don't have to repeat it in every package. In particular, it seems a bit strange to reimplement it in every package for Vector{NamedTuple} even though the only difference is how the samples are converted to a NamedTuple. But one could, e.g., also have a generic version for MCMCChains.Chains in MCMCChains with the basic structure + an interface for other packages to convert the samples, retrieve the names, the log-evidence + save the state, sampler, and model in a standardized way (and not different in every package).

This PR contains a very generic implementation for any desired vector-valued output.

[devmotion]

However, for AdvancedMH this would mean that the keyword argument param_names wouldn't be available anymore for Vector{NamedTuple} output. I'm wondering if that would be an issue? I guess users could still change the names afterwards (even for Chains) but requires an additional step?

[devmotion]

Ah wait, I guess one could just define convert(::Type{NamedTuple{names}}, ::Transition) in NamedTuples and then use Vector{NamedTuple{names}} as output type :+1:

Edit: But then one would have to include :lp in the names...

Edit 2: Could of course always assume that names does not include :lp - which is weird though since then the output wouldn't actually be of the stated type.

[codecov[bot]]

Codecov Report

Merging #46 into master will increase coverage by 0.03%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #46      +/-   ##
==========================================
+ Coverage   97.61%   97.65%   +0.03%     
==========================================
  Files           6        6              
  Lines         126      128       +2     
==========================================
+ Hits          123      125       +2     
  Misses          3        3              

Impacted Files	Coverage Δ
src/interface.jl	92.85% <100.00%> (+1.19%)	:arrow_up:

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[yebai]

@devmotion I fixed a merge conflict. Not sure it is what you intended to do. Pls, take a look anyway.

[devmotion]

Thanks, looks good to me!