feat(dart): use minimum SDK version for packages that use SDK for package version

[DmitriyLewen]

Description

Some dart packages use SDK version as package versions. But pubspec.lock and pubspec.yaml files contain version range for SDK. More details here - https://github.com/aquasecurity/trivy/discussions/5984#discussioncomment-8229400

### Tasks
- [x] use minimum SDK version for packages that use SDK for package version
- [x] add log message about using minimum SDK version from range

Discussed in https://github.com/aquasecurity/trivy/discussions/5984