[NFC][DirectX] Refactor mcdbc root parameters representation to support out of order storage.

[joaosaffran]

Refactor mcdbc root parameters representation to support out of order storage of parameters.

AC:

• remove union usage from mcdxbc
• propose new solution that doesn't really on union.
• Parameters don't need to be store in order, but must be written in order when serializing to dxcontainer.