feat(package_info_plus)!: Switch to SHA-256 for buildSignature on Android

[miquelbeltran]

Description

• As discussed in [Bug]: Insecure hashing algorithm SHA1 used #2833, the use of SHA-1 should be avoided.
• Besides, some security analysis tools may give a warning when analyzing the android APK for using SHA1.
• This change encourages users to switch to SHA-256 for the application certificate fingerprint verification.
• An alternative solution to this problem would be to remove the buildSignature completely, but I'd avoid doing that since we can use SHA-256 instead.

Thanks to @vitoramaral10 for the heads-up and providing the code!

Related Issues

• Fixes [Bug]: Insecure hashing algorithm SHA1 used #2833

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.