ShellPkg/DynamicCommand: add HttpDynamicCommand

ShellPkg/DynamicCommand: add HttpDynamicCommand

Introduce an http client utilizing EDK2 HTTP protocol, to
allow fast image downloading from http/https servers.
HTTP download speed is usually faster than tftp.
The client is based on the same approach as tftp dynamic command, and
uses the same UEFI Shell command line parameters. This makes it easy
integrating http into existing UEFI Shell scripts.
Note that to enable HTTP download, feature Pcd
gEfiNetworkPkgTokenSpaceGuid.PcdAllowHttpConnections must
be set to TRUE.
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2860

Signed-off-by: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>
Cc: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Nd <nd@arm.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>