openharmony-standard: Fix reuse of openharmony-standard sstate in CI

This fixes the problem that have caused us to always rebuilding openharmony-standard recipe in CI, even if no changes would seem to require it.

The fix is to rewrite the SRC_URI variable to not include git revisions but use SRCREV_* variables for that instead, and then setting up SRCREV_FORMAT appropriately to allow expansion of SRCPV with a meaningful and correct value.

Related to eclipse/oniro-core/meta-openharmony#62