build: upgrade JDK version to 18 for share_plus Android build

[imguptaharsh]

Description

This pull request updates the JDK version from 17 to 18 in the share_plus package's Android build configuration. This change affects both the compileOptions and kotlinOptions in the build.gradle file, where the source and target compatibility settings are updated to JavaVersion.VERSION_18 and jvmTarget to '18'. This update was motivated by the need to utilize the latest language features offered by JDK 18, improve performance, and ensure greater security compliance.

Related Issues

• Fix [Bug][Web]: Cannot build web when package_info_plus is in pubspec.yaml #987 (Example issue number for JDK upgrade necessity)

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits: chore: update JDK version to 18 in share_plus.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files, as this is a build environment change, not a functional change.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

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

This update to JDK 18 is a backend change that does not affect the exposed functionality or interfaces of the share_plus plugin; therefore, it does not require users to alter their existing applications. This update is intended to streamline development by adopting newer development tools and enhancements in JDK 18.

[vbuberen]

You need to learn about Java versions more, because what you did in this PR is switch from Java 17 to Java 8 in the project.

Closing as invalid.