Modifying default variables and config

Renamed variables for defaults:
- flatpak_method -> default_flatpak_method: system
- defaults.paths.prefix -> default_install_prefix: /usr/local
New variables:
- default_install_method: package

tasks/pkgs/alacritty.yml

@@ -32,7 +32,6 @@
           ansible.builtin.set_fact:
             alacritty_method: source
             alacritty_src_install:
-              cargo_install_type: source
               cargo_build_flags:
                 - --release
               name: "{{ alacritty_pkgname }}"
@@ -97,7 +96,6 @@
               - python3
               - desktop-file-utils
 # }}}
-
 - name: Append alacritty installation
   block:
     - name: Append alacritty to pkg_cargo