Add 4 APIs to DevicePathLib: ConvertDeviceNodeToText, ConvertDevicePathToText, ConvertTextToDeviceNode and ConvertTextToDevicePath.
Add a new instance of DevicePathLib which tries to locate the protocol and if it's not found, it uses the internal functions.

Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg@14504 6f19259b-4bc3-4df7-8a09-765794883524