ShellPkg/ShellProtocol.c: Fix case sensitivity in GetAlias and SetAlias
    
    ShellCommandIsOnAliasList is case insensitive, but GetAlias and SetAlias use the
    UEFI variable services, which are case sensitive.
    
    Force alias names to lowercase to get around this.
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Brendan Jackman <Brendan.Jackman@arm.com>
    Reviewed-By: Olivier Martin <olivier.martin@arm.com>
    Reviewed-by: Jaben Carsey <Jaben.carsey@intel.com>
    
    
    
    git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15270 6f19259b-4bc3-4df7-8a09-765794883524