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/localcachelayer/main_test.go

@@ -100,6 +100,12 @@ func getMockStore() *mocks.Store {
 	mockChannelStore.On("Get", channelId, false).Return(&fakeChannelId, nil)
 	mockStore.On("Channel").Return(&mockChannelStore)
 
+	mockChannelsMemberCount := map[string]int64{
+		"channel1": 10,
+		"channel2": 20,
+	}
+	mockChannelStore.On("GetChannelsMemberCount", []string{"channel1", "channel2"}).Return(mockChannelsMemberCount, nil)
+
 	mockPinnedPostsCount := int64(10)
 	mockChannelStore.On("GetPinnedPostCount", "id", true).Return(mockPinnedPostsCount, nil)
 	mockChannelStore.On("GetPinnedPostCount", "id", false).Return(mockPinnedPostsCount, nil)