Revert "Partially revert the usage of string enum."

This reverts commit e4a5cdbd95d97e4a1c2be9dea889a2ced922595f.

Reason for revert: The dashboard number doesn't seem to recover.

Bug: b/289956225
Bug: b/283858001
Change-Id: I118d301f4e3543f89d54251d3f45b4e09c71c44c
Test: forrest test
1 file changed