MdeModulePkg: UefiBootManagerLib to handle LoadFile DevicePath

MdeModulePkg: UefiBootManagerLib to handle LoadFile DevicePath

UEFI Spec HTTP Boot Device Path, after retrieving the boot resource
information, the BootURI device path node will be updated to include
the BootURI information. It means the device path on the child handle
will be updated after the LoadFile() service is called.

To handle this case, UefiBootManagerLib BmGetLoadOptionBuffer API
is updated as the below:
1) Get Device handle based on Device Path
2) Call LoadFile() service (GetFileBufferByFilePath() API) to get Load File Buffer.
3) Retrieve DevicePath from Device handle

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17798 6f19259b-4bc3-4df7-8a09-765794883524