NetworkPkg/DxeHttpLib: Migrate HTTP header manipulation APIs
    
    Move HTTP header manipulation functions to DxeHttpLib from
    HttpBootSupport.c. These general functions are used by both
    Http BOOT and RedfishLib (patches will be sent later).
    
    Signed-off-by: Abner Chang <abner.chang@hpe.com>
    
    Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
    Cc: Jiaxin Wu <jiaxin.wu@intel.com>
    Cc: Siyuan Fu <siyuan.fu@intel.com>
    Cc: Fan Wang <fan.wang@intel.com>
    Cc: Jiewen Yao <jiewen.yao@intel.com>
    Cc: Nickle Wang <nickle.wang@hpe.com>
    Cc: Peter O'Hanley <peter.ohanley@hpe.com>
    Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>