Make strict loading configurable in `Fabric.load()`

[awaelchli]

Description & Motivation

We added a new API for loading in Fabric in #16434. The loading of the module parameters currently uses just strict=True.

Pitch

Make it an argument. See todo notes in code here:
https://github.com/Lightning-AI/lightning/blob/39acb81b9bd01139f7cead31c673f25ba330f2f1/src/lightning_fabric/strategies/strategy.py#L270-L273

and here:

https://github.com/Lightning-AI/lightning/blob/39acb81b9bd01139f7cead31c673f25ba330f2f1/src/lightning_fabric/strategies/strategy.py#L281-L282

This may not be valid for all strategies. Thus, the argument type should probably be Optional[bool] = None.

Alternatives

No response

Additional context

No response

cc @Borda @carmocca @justusschock @awaelchli