Change to use package name for link type notation

[r-ralph]

Flags that exist in other modules can be linked by module-name:flag-name, and for this purpose, there is logic to get the package name from the module name.
It uses Task.getProject(), but it'll be deprecated (only for task phase) and it cannot be used from Gradle 9.0.
Therefore, to avoid having to subtract the package name from the module name, the specification of the link notation should be changed so that the package name is directly described.

Breaking Changes

Link type notation is changed as following:

AS-IS

module-name:flag_name

TO-BE

package.name:flag_name

[ganadist]

LGTM