fix(sidenav): correct animation from closed to locked open (#9833)
fix(sidenav): correct animation from closed to locked open (#9833)

sidenav was missing CSS a pre-animation state when transitioning
from closed to locked open

* Add CSS for missing pre-animation state
* Add comments to clarify animation logic

Fixes #9425
clshortfuse/material,david-gang/material,Frank3K/material,david-gang/material,ServiceManagementGroup/material,graingert/material,SamDLT/material,ilovett/material,vertazzar/material,DevVersion/material,imjoeco/material,ServiceManagementGroup/material,Frank3K/material,Splaktar/material,angular/material,imjoeco/material,daniel-nagy/material,ilovett/material,clshortfuse/material,angular/material,marekmicek/material,vertazzar/material,david-gang/material,miguelcobain/material,angular/material,ServiceManagementGroup/material,imjoeco/material,miguelcobain/material,profoundry-us/material,bluebirdtech/material,profoundry-us/material,pwistbac/material,marekmicek/material,oostmeijer/material,bluebirdtech/material,hayloft/material,SamDLT/material,SamDLT/material,daniel-nagy/material,daniel-nagy/material,vertazzar/material,DevVersion/material,imjoeco/material,miguelcobain/material,oostmeijer/material,pwistbac/material,graingert/material,ilovett/material,ServiceManagementGroup/material,SamDLT/material,DevVersion/material,vertazzar/material,crisbeto/material,miguelcobain/material,Splaktar/material,pwistbac/material,crisbeto/material,hayloft/material,DevVersion/material,clshortfuse/material,david-gang/material,marekmicek/material,graingert/material,Splaktar/material,bluebirdtech/material,clshortfuse/material,crisbeto/material,Splaktar/material,daniel-nagy/material,graingert/material,bluebirdtech/material,Frank3K/material,Frank3K/material,hayloft/material,pwistbac/material,oostmeijer/material,hayloft/material,profoundry-us/material,oostmeijer/material,marekmicek/material,profoundry-us/material,angular/material,ilovett/material,crisbeto/material