[PWGCF] Add flowDeltav1SP task

[annetkonings]

flowDeltav1SP.cxx calculates the directed flow with the spectator plane method for pions, kaons, protons. This is an extension of Noor Koster's flowSP.cxx.
The pull request does the following:

• adds flowDeltav1SP.cxx to PWGCF/Flow/Tasks;
• registers the workflow in PWGCF/Flow/Tasks/CMakeLists.txt.
  It is supposed to be run with zdcQVectors.cxx.

[github-actions]

O2 linter results: ❌ 1 errors, ⚠️ 2 warnings, 🔕 0 disabled

[annetkonings]

I named the main struct in this task flowDeltav1SP, where SP stands for spectator plane. Therefore the source file would need to remain flowDeltav1SP.cxx to satisfy the workflow-file naming check. However, the O2 linter now asks for the file to be named flowDeltav1Sp. I saw that flowSP and flowGF also have this capital letter issue. What is the recommendation here: use flowDeltav1SP.cxx everywhere or rename everything flowDeltav1Sp.cxx?

[lubynets]

I named the main struct in this task flowDeltav1SP, where SP stands for spectator plane. Therefore the source file would need to remain flowDeltav1SP.cxx to satisfy the workflow-file naming check. However, the O2 linter now asks for the file to be named flowDeltav1Sp. I saw that flowSP and flowGF also have this capital letter issue. What is the recommendation here: use flowDeltav1SP.cxx everywhere or rename everything flowDeltav1Sp.cxx?

The struct name flowDeltav1Sp has an advantage that the field in .json config (and configuration window in Hyperloop) will be more reading-friendly and not contain an extra hyphen: flow-deltav1-sp vs flow-deltav1-s-p.