Summary:
X-link: facebookincubator/zstrong#1036

X-link: facebook/fboss#285

__Why__
1. This is pre-req for other services to validate "PM generated data". e.g `platform_manager::ConfigValidator().isValidSlotPath(...)`
2. Beefing up SlotPath validation. See T205471819 more details.

__What__
1. Dropped ConfigValidator call in `Utils::parseDevicePath` because we can assume that config paths are valid. If ill-input is provided, unexpected behaviour.
2. Added additional regex for group capturing because it doesn't seem to work with a single regex for some reason...
3. Added topological validation on slot path.

__Next__
1. DeviceName validation. basically does device definition exist in the slot path?
2. Suppose VersionedPmUnit...

Reviewed By: somasun

Differential Revision: D64798493

fbshipit-source-id: 9ca1936bf81250bda1fc6b9d800221055b6b2f48