📝 Update docs for Query Params and String Validations, remove obsolete Ellipsis docs (...)

Pydantic and FastAPI discourage the use of Ellipsis (...) for a while now, any code using Ellipsis should be updated to instead not have any default parameter, which conveys the same meaning of making the parameter required.

The docs have been updated to not use nor recommend Ellipsis and instead use the more modern and supported form (just not declaring a default value).

The old examples were targetting Pydantic v1 only, and were not tested, so this hasn't been fully supported for a while.

This also updates and modernizes those same docs, to use the newer version of the syntax in the examples, prioritizing Python 3.10+.