update plugin to kotlin k2 - see email from Roni

[shalom938]

This task is now only validating that there are no issues when K2 is enabled

We don't use the analyze-api of kotlin compiler. but we do need to make sure our plugin is compatible with K2 and that there are no issues when K2 is enabled.

added to plugin.xml the tag that confirms that the plugin is K2 compatible

<extensions defaultExtensionNs="org.jetbrains.kotlin">
    <supportsKotlinPluginMode supportsK2="true" />
</extensions>

see https://kotlin.github.io/analysis-api/migrating-from-k1.html