Sync part of patches r14505, r14519 and r14558 from main trunk.
1. Update all the code to consume the ConvertDevicePathToText, ConvertDevicePathNodeToText, ConvertTextToDevicePath and ConvertTextToDeviceNode APIs in DevicePathLib.
2. OvmfPkg: Use the new DevicePathLib for all platforms.

git-svn-id: svn://svn.code.sf.net/p/edk2/code/branches/UDK2010.SR1/OvmfPkg@14643 6f19259b-4bc3-4df7-8a09-765794883524