Consider exposing more functionality in `devtools_app_shared`

[kenzieschmoll]

Some suggestions based on the creation of shared_preferences_tool: https://github.com/flutter/packages/pull/6749

• [x] DevToolsClearableTextField: https://github.com/flutter/devtools/blob/master/packages/devtools_app/lib/src/shared/common_widgets.dart#L839
  • done in https://github.com/flutter/devtools/pull/7979
• [x] RoundedDropdownButton: https://github.com/flutter/devtools/blob/master/packages/devtools_app/lib/src/shared/common_widgets.dart#L755
  • done in https://github.com/flutter/devtools/pull/7979
• [ ] search and filter UI elements
• [x] utilities like caseInsensitiveFuzzyMatch: https://github.com/flutter/devtools/blob/master/packages/devtools_app/lib/src/shared/primitives/utils.dart/#L959
  • done in https://github.com/flutter/devtools/pull/7979