refactor: expand glob imports

[joshka]

Consensus is that explicit imports make it easier to understand the example code. This commit removes the prelude import from all examples and replaces it with the necessary imports, and expands other glob imports (widget::, Constraint::, KeyCode::*, etc.) everywhere else. Prelude glob imports not in examples are not covered by this PR.

See https://github.com/ratatui-org/ratatui/issues/1150 for more details.

[EdJoPaTo]

Given that there are 4 warnings remaining when enabling (= removing the allow) of wildcard_imports (one in the examples), should it just be enabled in this PR too?

https://github.com/ratatui-org/ratatui/blob/74a32afbaef8851f9462b27094d88d518e56addf/Cargo.toml#L77

Edit: 5 including https://github.com/ratatui-org/ratatui/blob/74a32afbaef8851f9462b27094d88d518e56addf/src/widgets/scrollbar.rs#L7

[joshka]

wildcard_imports = "allow"

b82ccc28e

[joshka]

This helps a lot with reading code without an IDE ✨

Maybe remove the "all" from the title as prelude::* is still used in the lib itself. Also, this is a "refactor:" as it adapts the source code while maintaining the behavior? 🤔

done and done. Also fixed a doc lint