[PWGHF] Add mini trees to Ds task

[fchinu]

This PR adds the possibility to produce very small trees to be used in the analysis.
During previous presentations at the PAG, it was requested to also check the distribution of some topological variables, so I added the possibility to extend the mini trees with few other columns.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 0 disabled

[vkucera]

Hi @fchinu , please clarify the motivation for adding the trees. There already are workflows to store trees.

[fchinu]

Hi @vkucera! I updated the description. I add here that since these small trees can be used directly for analyses I thought of adding them to the task output, while other tasks produce very large output trees containing many variables, and are usually run on small datasets for model training. These trees can be in principle a replacement of the output sparses, which we know of having few problems for large datasets (e.g. they can't be merged for a size > 1 GB), also allowing the users to have the possibility to perform an unbinned analysis