This PR aims at several things:
1. Use pub_semver to check a version in pubspec.yaml meets the requirements specified in https://semver.org/.
2. Don't limit build-number/build-name as a fixed format. Instead, validate it according to the target(ios/android).
3. Make sure that build-number/build-name are always validated no matter it's specified by the `flutter command` or version in pubspec.yaml.
Fixes#27589
