[MM-37013] Async job to fix CRT channel unreads (#18340)

Summary
The addition of the TotalMsgCountRoot and MsgCountRoot columns to support CRT caused several issues with previously read threads and channels being marked as unread. Previously we attempted to fix this purely in a SQL migration [MM-35345][MM-35494] fixes for incorrect mentions and unreads for threads and channels #17803 but that turned out to be too heavy and it was decided to break up some of the fixes into async jobs.
This PR implements an async job to mark channels as read if there are no user posts since the last time the user viewed the channel. 

Ticket Link
https://mattermost.atlassian.net/browse/MM-37013

store/storetest/mocks/ChannelStore.go

@@ -582,6 +582,29 @@ func (_m *ChannelStore) GetByNames(team_id string, names []string, allowFromCach
 	return r0, r1
 }
 
+// GetCRTUnfixedChannelMembershipsAfter provides a mock function with given fields: channelID, userID, count
+func (_m *ChannelStore) GetCRTUnfixedChannelMembershipsAfter(channelID string, userID string, count int) ([]model.ChannelMember, error) {
+	ret := _m.Called(channelID, userID, count)
+
+	var r0 []model.ChannelMember
+	if rf, ok := ret.Get(0).(func(string, string, int) []model.ChannelMember); ok {
+		r0 = rf(channelID, userID, count)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]model.ChannelMember)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string, string, int) error); ok {
+		r1 = rf(channelID, userID, count)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetChannelCounts provides a mock function with given fields: teamID, userID
 func (_m *ChannelStore) GetChannelCounts(teamID string, userID string) (*model.ChannelCounts, error) {
 	ret := _m.Called(teamID, userID)

store/storetest/mocks/PostStore.go

@@ -635,6 +635,29 @@ func (_m *PostStore) GetSingle(id string, inclDeleted bool) (*model.Post, error)
 	return r0, r1
 }
 
+// GetUniquePostTypesSince provides a mock function with given fields: channelId, timestamp
+func (_m *PostStore) GetUniquePostTypesSince(channelId string, timestamp int64) ([]string, error) {
+	ret := _m.Called(channelId, timestamp)
+
+	var r0 []string
+	if rf, ok := ret.Get(0).(func(string, int64) []string); ok {
+		r0 = rf(channelId, timestamp)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]string)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string, int64) error); ok {
+		r1 = rf(channelId, timestamp)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // HasAutoResponsePostByUserSince provides a mock function with given fields: options, userId
 func (_m *PostStore) HasAutoResponsePostByUserSince(options model.GetPostsSinceOptions, userId string) (bool, error) {
 	ret := _m.Called(options, userId)