NetworkPkg: Add PCDs for HTTP DNS RetryCount and RetryInterval

NetworkPkg: Add PCDs for HTTP DNS RetryCount and RetryInterval

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3889

Currently the HTTP DNS Retry Interval is 2 second and no retry attempt.
If DNS response can't arrive in 2 second, the DNS request is failed,
and then HTTP boot is failed.
In order to resolve this issue, Add PCDs to support RetryCount
and RetryInterval configured in Platform.

Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Wu Jiaxin <jiaxin.wu@intel.com>
Signed-off-by: Heng Luo <heng.luo@intel.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>