[keyserver/lib] update farcaster channel tag blob payload to include keyserver id

Summary:
While working on the auto-join communities feature, I discovered an issue where the commCommunityID in the downloaded blob payload did not have the keyserverID:

farcasterChannelTagBlobs [
	{
		"commCommunityID": "83887",
		"farcasterChannelID": "comm"
	},
	{
		"commCommunityID": "145350",
		"farcasterChannelID": "memes"
	},
	{
		"commCommunityID": "83887",
		"farcasterChannelID": "farcaster"
	},
	{
		"commCommunityID": "83885",
		"farcasterChannelID": "founders"
	}
]

However, the the thread ids in the threadInfos look like this: 256|83843, where the keyserver id is appended to the front of the thread id and the two ids are separated by a pipe character. This diff updates the value of commCommunityID to follow this convention

Test Plan: flow + confirmed that the creating + updating + deleting farcaster tag all still worked

Reviewers: tomek, kamil, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12063