Ensure compatibility with older Kotlin consumers

[omarismail94]

We delegate the build configuration to Tapmoc and set the Kotlin version to 2.1 as the library uses APIs from this version that do not exist in 2.0.

One caveat:
project.configureJavaCompatibility(8) is not used as the code would compile with JDK 8. This will fail as RealBufferedSource.kt uses a Java API not available in Java 8: InputStream.transferTo. To use project.configureJavaCompatibility, the min supported Java version would need to be bumped to 11

TESTED: ./gradlew clean check . I also published to local repository and checked the .module files for the JVM and Android artifacts and the kotlin-stdlib was correctly set to 2.1.21

[swankjesse]

I like the effect but wow, this requires so much work.

[JakeWharton]

Need to use Tapmoc plugin. Much easier.

[omarismail94]

the tapmoc plugin does not work with KMP. I tried it locally, and it adds both the the KGP kotlin-stdlib  and the one set for compatibility (2.1.21) in the module file of the KMP targets:

"dependencies": [
        {
          "group": "org.jetbrains.kotlin",
          "module": "kotlin-stdlib",
          "version": {
            "requires": "2.2.21"
          }
        },
        {
          "group": "org.jetbrains.kotlin",
          "module": "kotlin-stdlib",
          "version": {
            "requires": "2.1.21"
          }
        }

For now, Ill add the plugin to the samples project (which isn't published), but keep the current behaviour I have

[omarismail94]

@JakeWharton @swankjesse tests now pass.

Jake - if you think tapmoc can still work, I can open it as a feature request issue against the repo. For now, Im hoping itd be fine to merge as is

[omarismail94]

@JakeWharton Actually, ignore my previous comment. I migrated to Tapmoc, and wow, the code is so much simpler!

One caveat:
project.configureJavaCompatibility(8) is not used as the code would compile with JDK 8. This will fail as RealBufferedSource.kt uses a Java API not available in Java 8: InputStream.transferTo. To use project.configureJavaCompatibility, the min supported Java version would need to be bumped to 11