Define step-0 for vintf finalization

Define `vintf` state that have completed vintf finalization only.
Only if FINAL_STATE is 'unfinalized' run the vintf finalization
process to finalize vintf.
The new step-0 only runs the vintf finalization.

Ignore-AOSP-First: trunk-stable changes (b/304316873)

Bug: 318883690
Test: build-step-0.sh && build/soong/soong_ui.bash \
    --make-mode TARGET_PRODUCT=cf_x86_64_phone TARGET_RELEASE=fina_0 \
    TARGET_BUILD_VARIANT=userdebug droid dist
Change-Id: If3525f38204fa546744b9ccf8dc9e63711823abd