Move get_window_size factor of merged_s2s as untracked configuration

[dachengx]

Before you submit this PR: make sure to put all operations-related information in a wiki-note, a PR should be about code and is publicly accessible

What does the code in this PR do / what does it improve?

The original factor is 5. This PR moves it to an untracked context configuration, because in reprocessing we might want to change it, but better without changing the source code.

It is trying to resolve: AxFoundation/strax#490

This PR will not change the result of MergedS2s. It will not change the lineage either.

Can you briefly describe how it works?

Can you give a minimal working example (or illustrate with a figure)?

Please include the following if applicable:

• Update the docstring(s)
• Update the documentation
• Tests to check the (new) code is working as desired.
• Does it solve one of the open issues on github?

Notes on testing

• Until the automated tests pass, please mark the PR as a draft.
• On the XENONnT fork we test with database access, on private forks there is no database access for security considerations.

All italic comments can be removed from this template.

[coveralls]

coverage: 93.564% (+0.02%) from 93.541% when pulling 81adf1d on merged_s2s_factor into a952805 on master.

[WenzDaniel]

Thanks, from a technical point of few it should be fine.

[FaroutYLq]

Thanks! Looks good to me but I would still wait for green light from @WenzDaniel.

[dachengx]

Thanks, both of you!