Std automatic timerange

[mnurisso]

PR description:

Utility for automatic detection of the most reasonable timespan for the standard deviation evaluation, to be used in diagnostics.

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• Tests are included if a new feature is included.
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• If a source is added, the experiment table on the wiki is updated.
• environment.yml and pyproject.toml are updated if needed, together with the lumi installation tool.

[mnurisso]

Not clear if it is needed. If a use case is found we merge it.