SerializeFlags is a namespace.

The SerializeFlags becomes a namespace that contains
the original class definition under type SerializeFlags::Type
and static constants.

Consequently, all SeralizeFlags methods can
now be constexpr.

Also added static tests.

Test: libvintf_test
Test: vintf_object_test
Bug: 110711640
Change-Id: I786a1f77e19defc2ab2d025de3ed7cfe48f4fbce
7 files changed