Migrate ExcludeInternalDoclet to latest artifacts from javadoc-tools

[alexander-yevsyukov]

Currently the ExcludeInternalDoclet which is used for adding filtering doclet to a Gradle project uses the version, which was introduced in base long ego.

The API of newer version of Javadoc tools introduces different packages and names. E.g. io.spine.tools.javadoc.ExcludeInternalDoclet became io.spine.tools.javadoc.doclet.ExcludeInternal.

We need to migrate to newer API in two steps:

• Step 1. Update ExcludeInternalDoclet.kt to use new API.

• Step 2. Turn ExcludeInternalDoclet.kt into a part of javadoc-filter artifact, having it as a Gradle plugin, which would be published at Gradle Plugin Portal.

[alexander-yevsyukov]

@armiol, FYI.