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/plugin/checker/internal/test/invalid/invalid.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package invalid
+
+type API interface {
+	// ValidMethod is a fake method for testing the
+	// plugin comment checker with a valid comment.
+	//
+	// Minimum server version: 1.2.3
+	ValidMethod()
+
+	// InvalidMethod is a fake method for testing the
+	// plugin comment checker with an invalid comment.
+	InvalidMethod()
+}
+
+type Helpers interface {
+	// Minimum server version: 1.1
+	LowerVersionMethod()
+
+	// Minimum server version: 1.3
+	HigherVersionMethod()
+}
+
+type HelpersImpl struct {
+	api API
+}
+
+func (h *HelpersImpl) LowerVersionMethod() {
+	h.api.ValidMethod()
+}
+
+func (h *HelpersImpl) HigherVersionMethod() {
+	h.api.ValidMethod()
+}