ShellPkg: Fix EFI_SHELL_PROTOCOL to contain new members from UEFI Shell 2.1 spec
- Removes EFI_SHELL_PROTOCOL21
- Adds RegisterGuidName, GetGuidName, GetGuidFromName, and GetEnvEx to EFI_SHELL_PROTOCOL

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chris Phillips <chrisp@hp.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellPkg@15818 6f19259b-4bc3-4df7-8a09-765794883524