License update - Batch 52

[mossmana]

Updates the license headers for:

1. packages/devtools_app_shared/lib/src/ui/buttons.dart
2. packages/devtools_app_shared/lib/src/ui/common.dart
3. packages/devtools_app_shared/lib/src/ui/dialogs.dart
4. packages/devtools_app_shared/lib/src/ui/flex_split_column.dart
5. packages/devtools_app_shared/lib/src/ui/icons.dart
6. packages/devtools_app_shared/lib/src/ui/split_pane.dart
7. packages/devtools_app_shared/lib/src/ui/text_field.dart
8. packages/devtools_app_shared/lib/src/ui/theme/_ide_theme_desktop.dart
9. packages/devtools_app_shared/lib/src/ui/theme/_ide_theme_web.dart
10. packages/devtools_app_shared/lib/src/ui/theme/ide_theme.dart
11. packages/devtools_app_shared/lib/src/ui/theme/theme.dart
12. packages/devtools_app_shared/lib/src/ui/ui_utils.dart
13. packages/devtools_app_shared/test/ui/common_test.dart
14. packages/devtools_app_shared/test/ui/flex_split_column_test.dart
15. packages/devtools_app_shared/test/ui/ide_theme_test.dart
16. packages/devtools_app_shared/test/ui/split_pane_test.dart
17. packages/devtools_app_shared/test/ui/theme_test.dart

#8216

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read the [Flutter Style Guide] recently, and have followed its advice.
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or there is a reason for not adding tests.