Set the update channel list (Recommendation Setting)

Default policy is empty. If this policy is empty or invalid, client will set Slow and Fast as the default update channel list. If this policy is a valid string, client will set the update channel list according to the string. The format of this string should be {channel id}:{channel name} and use semicolon to separate different channels, for example: "0:Slow" will add Slow to the update channel list, "0:Slow;1:Fast" will add Slow and Fast to the update channel list. The following are the two public update channels: "0" - Slow "1" - Fast Note: 1.Slow will be added to the list even if it is not written to string. If this setting is not set, client will use the default setting.