SF: Decouple ID parsing from flags and sysprops

This change refactors parseDisplayIdentificationData to no longer
directly query the stable_edid_ids feature flag. Instead, it now accepts
a useStableEdidIds boolean parameter to control whether to generate a
stable ID from EDID or use the legacy port-based scheme.

This refactoring decouples the parsing logic from the global
FlagManager, making the function a more self-contained utility. It also
improves testability, as both code paths can now be tested by simply
passing true or false without needing to mock the feature flag state.

The call sites in HWComposer have been updated to read the flag and pass
the value down to the function, preserving the existing behavior.

Bug: 440590608
Flag: EXEMPT PURE_REFACTOR
Test: Presubmit
Change-Id: If2a4c4698de9884b9bcbec00cb8f4999023d0342