refactor(cli): simplify `features: Option<Vec<String>>` to `Vec<String>` (#14607)

* refactor: use empty vector for features instead of None

* refactor: reorder

* add change file

* comment: highlight places where serialization is used

* refactor: simplify serialization

* Update .changes/empty-vec-instead-of-none.md

* Update crates/tauri-cli/src/mobile/ios/mod.rs

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Co-authored-by: Tony <68118705+Legend-Master@users.noreply.github.com>