Support Gradle's `kotlinOptions.freeCompilerArgs`

Someone ran into this issue in Dagger when trying to set the module name via `kotlinOptions.freeCompilerArgs`: https://github.com/google/dagger/issues/4493.

In this case, using `kotlin.compilerOptions.moduleName` works (KSP supports this); however, it would be nice if KSP also checked the `freeCompilerArgs` as well. At the very least, consider checking the value and throwing an exception with an error message telling users to use the `kotlin.compilerOptions` API instead.

Start by tracing how KSP handles kotlin.compilerOptions.moduleName and the Gradle kotlinOptions.freeCompilerArgs input. Done means either supporting the module-name value from freeCompilerArgs or rejecting it with an error that directs users to the kotlin.compilerOptions API.

Written by the indexing model from the issue text.