ci: move public-api goldens to goldens directory (#35768)

Moves the public api .d.ts files from tools/public_api_guard to
goldens/public-api.

Additionally, provides a README in the goldens directory and a script
assist in testing the current state of the repo against the goldens as
well as a command for accepting all changes to the goldens in a single
command.

PR Close #35768

goldens/public-api/compiler-cli/error_code.d.ts

@@ -0,0 +1,35 @@
+export declare enum ErrorCode {
+    DECORATOR_ARG_NOT_LITERAL = 1001,
+    DECORATOR_ARITY_WRONG = 1002,
+    DECORATOR_NOT_CALLED = 1003,
+    DECORATOR_ON_ANONYMOUS_CLASS = 1004,
+    DECORATOR_UNEXPECTED = 1005,
+    DECORATOR_COLLISION = 1006,
+    VALUE_HAS_WRONG_TYPE = 1010,
+    VALUE_NOT_LITERAL = 1011,
+    COMPONENT_MISSING_TEMPLATE = 2001,
+    PIPE_MISSING_NAME = 2002,
+    PARAM_MISSING_TOKEN = 2003,
+    DIRECTIVE_MISSING_SELECTOR = 2004,
+    UNDECORATED_PROVIDER = 2005,
+    DIRECTIVE_INHERITS_UNDECORATED_CTOR = 2006,
+    SYMBOL_NOT_EXPORTED = 3001,
+    SYMBOL_EXPORTED_UNDER_DIFFERENT_NAME = 3002,
+    CONFIG_FLAT_MODULE_NO_INDEX = 4001,
+    CONFIG_STRICT_TEMPLATES_IMPLIES_FULL_TEMPLATE_TYPECHECK = 4002,
+    HOST_BINDING_PARSE_ERROR = 5001,
+    NGMODULE_INVALID_DECLARATION = 6001,
+    NGMODULE_INVALID_IMPORT = 6002,
+    NGMODULE_INVALID_EXPORT = 6003,
+    NGMODULE_INVALID_REEXPORT = 6004,
+    NGMODULE_MODULE_WITH_PROVIDERS_MISSING_GENERIC = 6005,
+    NGMODULE_REEXPORT_NAME_COLLISION = 6006,
+    NGMODULE_DECLARATION_NOT_UNIQUE = 6007,
+    SCHEMA_INVALID_ELEMENT = 8001,
+    SCHEMA_INVALID_ATTRIBUTE = 8002,
+    MISSING_REFERENCE_TARGET = 8003,
+    MISSING_PIPE = 8004,
+    WRITE_TO_READ_ONLY_VARIABLE = 8005,
+    DUPLICATE_VARIABLE_DECLARATION = 8006,
+    INJECTABLE_DUPLICATE_PROV = 9001
+}