[nova][sfe] Use PCPU and VCPU in One Instance

Hi,

We are proposing a Nova spec for the feature of creating an instance of mixed dedicated CPUs and shared CPUs and experience communities review. The spec link is https://review.opendev.org/#/c/668656/ and spec name is "Use PCPU and VCPU in One Instance".

I recognized that Nova Sepc for Train release is frozen, I'd like to request a spec freeze exception process and let the spec to be merged in train release.

I may have trouble in attending next week's team meeting, on Aug 1, so, please discuss in the email thread.

Thanks Huaqiang