use use modifiers specific functions to get/set modifiers

Summary:
use dedicated functions for modifiers instead of package values
Will land after core changes are landed

Reviewed By: scottcao

Differential Revision: D68898019

fbshipit-source-id: bb671db3b59f68bb8d92971737a1a71f09638e2f

prelude/cfg/modifier/set_cfg_modifiers.bzl

@@ -5,7 +5,7 @@
 # License, Version 2.0 found in the LICENSE-APACHE file in the root directory
 # of this source tree.
 
-load(":common.bzl", "MODIFIER_METADATA_KEY", "get_tagged_modifiers", "tagged_modifiers_to_json")
+load(":common.bzl", "get_tagged_modifiers", "tagged_modifiers_to_json")
 load(":types.bzl", "Modifier", "ModifierPackageLocation")  # @unused Used in type annotation
 
 def set_cfg_modifiers(
@@ -38,9 +38,9 @@ def set_cfg_modifiers(
     cfg_modifiers = cfg_modifiers or []
     extra_cfg_modifiers_per_rule = extra_cfg_modifiers_per_rule or {}
 
-    merged_modifier_jsons = read_parent_package_value(MODIFIER_METADATA_KEY)
+    merged_modifier_jsons = get_parent_modifiers()
 
-    # `read_parent_package_value` returns immutable values. `list()` makes it mutable.
+    # `get_parent_modifiers` returns immutable values. `list()` makes it mutable.
     merged_modifier_jsons = list(merged_modifier_jsons) if merged_modifier_jsons else []
 
     tagged_modifiers_list = get_tagged_modifiers(
@@ -50,10 +50,8 @@ def set_cfg_modifiers(
     )
     merged_modifier_jsons += [tagged_modifiers_to_json(tagged_modifiers) for tagged_modifiers in tagged_modifiers_list]
 
-    write_package_value(
-        MODIFIER_METADATA_KEY,
+    set_modifiers(
         merged_modifier_jsons,
-        overwrite = True,
     )
 
 def _get_package_path() -> str: