[native_assets_cli] Cleanup List from API (#1342)

Use `Iterable` over `List` in the public API:

* Immediately assigning lists into our own fields is dangerous, users might modify the list later instead of using methods on the API.
* Only giving `Iterable`s to users prevents us having to copy the list on returning a list. (Or we'd risk users modifying the internal list).

For `Map` we don't really have a different API type to signify this difference unfortunately. What we do in most of the API is:

* Have an `add(param1, param2)` method instead of using an `addAll(Map)`.
* Have a `lookupParam2(param1)` method instead of exposing a `Map`.
* But our constructors often still take maps, and we need to ensure we do a copyAll/addAll on those entries.

Author: dcharkes

pkgs/native_assets_cli/lib/src/api/build_output.dart

@@ -61,7 +61,7 @@ abstract final class BuildOutput {
   ///
   /// In dry runs, the assets for all [Architecture]s for the [OS] specified in
   /// the dry run must be provided.
-  Map<String, List<Asset>> get assetsForLinking;
+  Map<String, Iterable<Asset>> get assetsForLinking;
 
   /// The files used by this build.
   ///

pkgs/native_assets_cli/lib/src/api/link_config.dart

@@ -46,7 +46,7 @@ abstract class LinkConfig implements HookConfig {
     int? targetMacOSVersion,
     CCompilerConfig? cCompiler,
     BuildMode? buildMode,
-    List<String>? supportedAssetTypes,
+    Iterable<String>? supportedAssetTypes,
     int? targetAndroidNdkApi,
     required Iterable<Asset> assets,
     required LinkModePreference linkModePreference,
@@ -77,7 +77,7 @@ abstract class LinkConfig implements HookConfig {
     required String packageName,
     required Uri packageRoot,
     required OS targetOS,
-    List<String>? supportedAssetTypes,
+    Iterable<String>? supportedAssetTypes,
     required Iterable<Asset> assets,
     required LinkModePreference linkModePreference,
     Version? version,

pkgs/native_assets_cli/lib/src/api/link_output.dart

@@ -54,7 +54,7 @@ abstract final class LinkOutput {
   void addAssets(Iterable<Asset> assets);
 
   factory LinkOutput({
-    List<AssetImpl>? assets,
+    Iterable<AssetImpl>? assets,
     Dependencies? dependencies,
     DateTime? timestamp,
   }) =>

pkgs/native_assets_cli/lib/src/model/hook_output.dart

@@ -29,12 +29,14 @@ final class HookOutputImpl implements BuildOutput, LinkOutput {
 
   HookOutputImpl({
     DateTime? timestamp,
-    List<AssetImpl>? assets,
+    Iterable<AssetImpl>? assets,
     Map<String, List<AssetImpl>>? assetsForLinking,
     Dependencies? dependencies,
     Metadata? metadata,
   })  : timestamp = (timestamp ?? DateTime.now()).roundDownToSeconds(),
-        _assets = assets ?? [],
+        _assets = [
+          ...?assets,
+        ],
         _assetsForLinking = assetsForLinking ?? {},
         // ignore: prefer_const_constructors
         _dependencies = dependencies ?? Dependencies([]),