Set Change::Metadata on LayerMetadata update

Currently, on layer_state_t::eMetadataChanged, only
Change::GameMode is set. Hence, for other metadata changes
such as METADATA_OWNER_UID, METADATA_MOUSE_CURSOR,
etc. (used by ARC++), these doesn't get propagated until
`forceUpdate=true` or `gameMode` is updated.

This leaves ARC++ LayerFE receiving stale metadata, even
though "update" was received.

Bug: 339382668
Test: atest libsurfaceflinger_unittests
Change-Id: I8130c3505b9808a9aa04d1641dc1c22352d6bf87