Add track tree writer

[beomki-yeo]

This PR adds an event tree writer to records the value of various properties (truth particle information, fitting information, etc.)

One of the motivations is to compare the fitted momentum distribution between CPU and GPU:

In this PR, I only added trees for truth particle information and fitting results. We can add more in the future if necessary

[beomki-yeo]

@krasznaa Could you take a look?

[krasznaa]

🤔 I believe the code is a bit too over-complicated right now.

But let's start at the beginning. Let's not use a generic name like event_tree_writer for this class. It is doing a very specific thing. It writes data about the truth and reconstructed tracks. So let's call it something like: traccc::root::tracking_performance_file_writer. (I'm very open to a better name. My point is just to give it a little more concrete of a name.)

Then... I am on board with the general API of the current traccc::event_tree_writer class. But its implementation is unnecessarily complicated. Just make traccc::details::event_tree_writer_data (or whatever you rename it to) do the heavy lifting itself. There's no need for an extra layer of classes under that data class. It can just be the "data class", which itself would both hold the primitive variables that the output TTree is written with, and the code that deals with the TTree.

The "cache concept" for this writer is just not necessary. 🤔

But sure, with a better name, and some simplification, I'm very open to adding this to the project.

[beomki-yeo]

Thanks for the comments! I simplified the code now with different name