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

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

server/channels/store/store.go

@@ -222,6 +222,7 @@ type ChannelStore interface {
 	GetMember(ctx context.Context, channelID string, userID string) (*model.ChannelMember, error)
 	GetChannelMembersTimezones(channelID string) ([]model.StringMap, error)
 	GetAllChannelMembersForUser(userID string, allowFromCache bool, includeDeleted bool) (map[string]string, error)
+	GetChannelsMemberCount(channelIDs []string) (map[string]int64, error)
 	InvalidateAllChannelMembersForUser(userID string)
 	IsUserInChannelUseCache(userID string, channelID string) bool
 	GetAllChannelMembersNotifyPropsForChannel(channelID string, allowFromCache bool) (map[string]model.StringMap, error)