☔ Update all interactive samples/snippets for lint issues

[TahaTesser]

Following examples/code snippets need updates

Cookbook

Design

• [x] Export fonts from a package
• [x] Use a custom font

Effects

• [x] Create a download button
• [x] Create a nested navigation flow
• [x] Create a photo filter carousel
• [x] Create a staggered menu animation
• [x] Create an expandable FAB

Forms

• [x] Create and style a text field

Images

• [x] Display images from the internet
• [x] Fade in images with a placeholder
• [x] Work with cached images

Lists

• [x] Create a grid list
• [x] Create a horizontal list
• [x] Use lists

Navigation

• [x] Navigate to a new screen and back

Codelabs

• [x] Explicit animations
• [x] Implicit animations
• [x] Basic Flutter layout concepts

more to be added...

Describe the problem

Interactive sample/code snippets throw lint issue messages

Expected fix

Update interactive sample and code snippets

Additional context

No response

[TahaTesser]

Some PRs are ready to file but I will wait until flutter/website is ready to accept PRs

[TahaTesser]

Raising priority to medium as the list of examples is increasing and more pages on the websites need these updates than realized earlier.

[TahaTesser]

Closing as done, if there are anymore remaining, please file a new issue.