feat req: Allow all packages to define their own executable permissions for asset files

[xxxxxliil]

Some asset files in my project require executable permissions, so I adjusted the permissions as needed when adding them to the project. However, they lack executable permissions after a Flutter build. The current workaround is to manually set the permissions using the postinst hook, but this method does not comply with release packaging guidelines.

I want the executable permissions of asset files to be inherited from the original file by default, and for there to be a list that supports wildcard matching and setting file permissions.