MM42267: Add member count in the browse channel modal (#23800)

* add base for calling the endpoint

* add endpoint and handler

* update store and layers

* call the endpoint

* align types

* update app layers

* generate mocks

* complete handler

* finish store query

* add todos

* add ui for member count

* add selector

* add a todo

* add cache layer

* optimize calls in FE

* handle invalidation of the cache

* fix go style

* fix test

* use existing channel layer count

* fix import error

* delete unnecessary code

* write tests for channel cache layer

* fix testname

* fix mocks

* fix cache layer test

* fix a test

* really fix the test

* write more tests for server

* address PR comments

* remove comment

* rename more_channels to browse_channels

* fix style

* update snapshot

* add translations

* Revert "add translations"

This reverts commit 56476a5dabe357703ef02be9a38b3e88f5c8b1e7.

* add only related translations

* address PR review points

* add test

* fix test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/store/storetest/mocks/ChannelStore.go

@@ -910,6 +910,32 @@ func (_m *ChannelStore) GetChannelsByUser(userID string, includeDeleted bool, la
 	return r0, r1
 }
 
+// GetChannelsMemberCount provides a mock function with given fields: channelIDs
+func (_m *ChannelStore) GetChannelsMemberCount(channelIDs []string) (map[string]int64, error) {
+	ret := _m.Called(channelIDs)
+
+	var r0 map[string]int64
+	var r1 error
+	if rf, ok := ret.Get(0).(func([]string) (map[string]int64, error)); ok {
+		return rf(channelIDs)
+	}
+	if rf, ok := ret.Get(0).(func([]string) map[string]int64); ok {
+		r0 = rf(channelIDs)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(map[string]int64)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func([]string) error); ok {
+		r1 = rf(channelIDs)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetChannelsWithCursor provides a mock function with given fields: teamId, userId, opts, afterChannelID
 func (_m *ChannelStore) GetChannelsWithCursor(teamId string, userId string, opts *model.ChannelSearchOpts, afterChannelID string) (model.ChannelList, error) {
 	ret := _m.Called(teamId, userId, opts, afterChannelID)