feat: add support for package conflicts in alternatives

- Introduced a new `conflicts` field in the `Alternatives` struct to track conflicting packages.
- Updated database schema to include a `conflicts` table and related queries.
- Enhanced package specification handling to include conflicts in TOML serialization and deserialization.
- Modified the interactive package creation to allow input for conflicting packages.
- Updated source repository index creation to handle conflicts and added relevant statistics.
- Adjusted tests to cover new conflicts functionality in package alternatives.

src/package/packager.rs

@@ -171,6 +171,17 @@ impl Packager {
                     .collect(),
             ),
         );
+        map.insert(
+            "conflicts".to_string(),
+            toml::Value::Array(
+                self.spec
+                    .alternatives
+                    .conflicts
+                    .iter()
+                    .map(|s| toml::Value::String(s.clone()))
+                    .collect(),
+            ),
+        );
 
         // Add install-relevant dependency kinds for repo/runtime consumers.
         let mut deps = toml::map::Map::new();