[Request]: Fix mismatch between Dart and Flutter minimum versions across packages

### Plugin

all relevant packages

### Use case

While testing the local build environment for `connectivity_plus` using its stated minimum Flutter version (`3.7.0`), I encountered a version constraint mismatch.

Flutter `3.7.0` includes Dart SDK `2.19.0`. However, the package constraints require Dart `>=3.3.0 <4.0.0` (which implies a minimum of Flutter `3.19.0` or higher).

Attempt to pin the Flutter SDK to the documented minimum version using FVM:
```bash
fvm use 3.7.0
SDK Version : 3.7.0 has Dart SDK 2.19.0 does not meet the project constraints of >=3.3.0 <4.0.0.
This could cause unexpected behavior or issues.
```

### Proposal

Since the current Dart SDK constraints already implicitly require a much higher Flutter SDK, it should be safe to bump the minimum flutter version in pubspec.yaml across the affected packages to match the reality.