test(package): align LE tests with opt-in API from #9033

PR #9033 made AWS::LanguageExtensions local processing opt-in. Two API
changes broke three tests on this branch after the merge from develop:

- expand_language_extensions() now requires a keyword-only `enabled` arg
- PackageContext reads self._language_extensions_enabled, set in __init__

Pass enabled=True to expand_language_extensions in the two artifact-exporter
tests, and set _language_extensions_enabled on the PackageContext stub that
bypasses __init__ via __new__. All three tests exercise templates with
Transform: AWS::LanguageExtensions, so enabling LE is the intended behavior.

Author: bnusunny

tests/unit/commands/package/test_package_context.py

@@ -4524,6 +4524,10 @@ def setUp(self):
         self.ctx.code_signer = MagicMock()
         self.ctx.parameter_overrides = {}
         self.ctx._global_parameter_overrides = {}
+        # Language Extensions is opt-in (#9033); the buried-AWS::Include regression
+        # test exercises a template that uses Transform: AWS::LanguageExtensions,
+        # so enable LE expansion explicitly.
+        self.ctx._language_extensions_enabled = True
 
     def test_buried_aws_include_location_is_rewritten(self):
         from samcli.yamlhelper import yaml_parse

tests/unit/lib/package/test_artifact_exporter.py

@@ -2070,7 +2070,7 @@ def test_le_template_with_top_level_aws_include_merges_location(self):
 
             parameter_values = dict(IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES)
 
-            result = expand_language_extensions(template_dict, parameter_values)
+            result = expand_language_extensions(template_dict, parameter_values, enabled=True)
             self.assertTrue(result.had_language_extensions)
 
             template = Template(
@@ -2168,7 +2168,7 @@ def test_le_template_with_serverless_repo_metadata_merges_license_url(self):
 
             parameter_values = dict(IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES)
 
-            result = expand_language_extensions(template_dict, parameter_values)
+            result = expand_language_extensions(template_dict, parameter_values, enabled=True)
             self.assertTrue(result.had_language_extensions)
 
             template = Template(