refactor: rename aim to upm and extract appimage module

crates/upm-core/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "upm-core"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[lib]
+path = "src/lib.rs"
+
+[dependencies]
+base64.workspace = true
+fs2.workspace = true
+md5.workspace = true
+quick-xml.workspace = true
+reqwest.workspace = true
+serde.workspace = true
+serde_yaml.workspace = true
+sha2.workspace = true
+toml.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true