Remove "All right reserved" from all files (#10066)
Per guidance from legal on current preferred practice, remove "All rights reserved" from all LICENSE files and header blocks, and update the repo tool check accordingly.
[various] Update READMEs to reflect current OS support (#10470)
* Updates all READMEs to list the OS versions currently supported by the latest platform implementations.
* This is not necessarily the same as the OS version that the current version of the app-facing platform supports; for plugins where the app-facing package still supports Flutter 3.32, clients using Flutter 3.32 will get older versions of the platform implementations that are still compatible with iOS 12/Android API 21-23. However, the Flutter team no longer actively supports those versions, which is what we are choosing to reflect in READMEs. (In the future, we may want to move this information to platform implementation package READMEs, although that will make it harder to skim.)
* Updates all Android plugins that still listed a minSdkVersion of 21 to 24.
* This is a no-op for clients; all of these implementation packages already require Flutter 3.35, which can only build for 24+.
* This part is the Android version of https://github.com/flutter/packages/pull/10231, but no SDK changes were needed here. All the changes where we could make code changes were already done in https://github.com/flutter/packages/pull/9851.
Fixes https://github.com/flutter/flutter/issues/178757
## Pre-Review Checklist
[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.
[various] Enable warnings as errors, and all warnings, for Android lint (#3648)
For all Android plugins:
- Enable all warnings for lint
- Treat all warnings as errors for lint
This significantly increases the scope of issues that we'll catch in CI. To
allow enabling this without having to make tons of fixes first, so that
we get the incremental benefit immediately, this adds new baselines for
all plugins. We can incrementally clean those baselines up over time.
(In practice we haven't prioritized that, but it would be good to start
paying down that technical debt incrementally at some point.)
See https://github.com/flutter/flutter/issues/88011