Adds a gradle plugin for graalpy

[Sowasvonbot]

The plugin requires the java-Plugin. If it is not loaded, the plugin will apply it.

It adds to task in the graalpy section:

graalpy {
  generateManifest
  installPackages
}

It may be configured in the the build.gradle with the following settings:

graalPy {
    packages = ["tqdm==4.66.4", "ujson"] // default: []
    includeVfsRootDir = true // default: true. If true, the venv and home will be put into: org.graalvm.python.vfs
    pythonHome {
        includes = ["someRegex"] // default: [".*"]
        excludes = ["someRegex"] // default: []
    }
    pythonResourcesDirectory = file "path/to/some/dir" // default: $buildDir/python-generated
   // if no value is provided for the directory, it will also be added to the classpath and added to the jar
}

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[timfel]

@tomasstupka will review and integrate this :-)

[fniephaus]

Merged via https://github.com/oracle/graalpython/commit/bd0e25ed7ea3d012785760b82436cc3f41809541