Merge SolibSymlinkAction with SymlinkAction

`SolibSymlinkAction` should be turned into a factory that creates a `SymlinkAction` as their `execute` method is effectively identical. The benefit of this is that we'll have one fewer native action implementation.

Locate SolibSymlinkAction and SymlinkAction, then compare their execute methods and construction paths. Confirm that SolibSymlinkAction becomes a factory producing SymlinkAction and that the native action implementation count is reduced without changing execution behavior.

Written by the indexing model from the issue text.