[RPM] Support custom 'package_name' to control installation paths and binary naming

[eximius313]

Description:

Problem

Currently, the RPM maker rigidly ties the package name, installation directory, and executable command to the Flutter project name (appName). There is no way to override this, unlike the Deb maker which supports a package_name configuration field.

This limitation prevents developers from publishing packages with names different from their internal project names (e.g., publishing foo when the project is named foo_something) without ending up with mismatched paths or commands.

Proposal

Implement support for the package_name field in make_config.yaml for RPM, fully aligning it with the logic used in AppPackageMakerDeb.

Example Config:

rpm:
  package_name: foo # System name
  # ...

Result:
Even if the binary is foo_something, the user installs foo, runs foo in the terminal, and sees foo.desktop.