feat: Add Configurable Speed and Direction to Spinner Control

[KongJian520]

Description

This commit introduces two new properties for the Spinner control: speed and clockwise, allowing developers to customize the behavior of its rotation animation.

Major Changes

• Added speed: Option<f64> and clockwise: Option<bool> fields to the Spinner structure.
• Provided chainable speed() and clockwise() methods to facilitate setting these new properties.
• In the ui method of the Widget implementation, unwrap_or is used to set default values ​​for these two properties to ensure they work correctly even when not explicitly set.
• Modified the paint_at method signature to directly accept the processed speed and clockwise parameters to simplify the drawing logic.
• In order to avoid affecting the effect of the original component, I Modify the loading in the image component to Spinner::new().paint_at(ui, rect, 1.0, true);()

• I have followed the instructions in the PR template

[github-actions]

Preview available at https://egui-pr-preview.github.io/pr/7532-kongjian520feat-Spinner
Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

[KongJian520]

@lucasmerlin I'm ready, thanks for the review