TCPMv2: Consolidate common VDM behavior
TCPMv2: Consolidate common VDM behavior

Parse received VDM responses initially in parent state
PE_VDM_SEND_REQUEST and record the result. Handle that result in a
state-specific way in state-specific run functions.

Reduce flash size by 40 bytes on average (volteer RW: 28 bytes).

BUG=b:158572770
TEST=Observe discovery and DP/TBT setup traffic
BRANCH=none

Signed-off-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>
Change-Id: I46bbee663c713cbcef40df8bf39359a26c8d5e32
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2274643
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec