Expose public/ API as submodule (#23345)

* model -> public/model

* plugin -> public/plugin

* public/model/utils -> public/utils

* platform/shared/mlog -> public/shared/mlog

* platform/shared/i18n -> public/shared/i18n

* platform/shared/markdown -> public/shared/markdown

* platform/services/timezones -> public/shared/timezones

* channels/einterfaces -> einterfaces

* expose public/ submodule

* go mod tidy

* .github: cache-dependency-path, setup-go-work

* modules-tidy for public/ too

* remove old gomodtidy

server/public/model/plugin_status.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+const (
+	PluginStateNotRunning          = 0
+	PluginStateStarting            = 1 // unused by server
+	PluginStateRunning             = 2
+	PluginStateFailedToStart       = 3
+	PluginStateFailedToStayRunning = 4
+	PluginStateStopping            = 5 // unused by server
+)
+
+// PluginStatus provides a cluster-aware view of installed plugins.
+type PluginStatus struct {
+	PluginId    string `json:"plugin_id"`
+	ClusterId   string `json:"cluster_id"`
+	PluginPath  string `json:"plugin_path"`
+	State       int    `json:"state"`
+	Error       string `json:"error"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	Version     string `json:"version"`
+}
+
+type PluginStatuses []*PluginStatus