MM-13893: refactor config (#10230)

* refactor utils/config* to config/

* pull validateLdapFilter into app

* clean up Config/GetConfig/GetSanitizedConfig usage

Eliminate app.GetConfig() in favour of just using app.Config() directly,
but expose app.GetSanitizedConfig() for when the old behaviour was
required.

* web: isolate config setup

* TestInvitePeopleProvider: make config explicit

* regenerateClientConfig: avoid racey map access

* integrate watch flag into app.ConfigFile option

* make app.Option return an error

* release.mk: only cp static files from config/

* release.mk: fix cp static files from config/

* api4: TestPlugin cleanup

* s/c/cfg/ for clarity

* fix merge conflict

* testlib: allow customization of testlib driver name

services/mailservice/mail_test.go

@@ -12,6 +12,7 @@ import (
 	"net/mail"
 	"net/smtp"
 
+	"github.com/mattermost/mattermost-server/config"
 	"github.com/mattermost/mattermost-server/model"
 	"github.com/mattermost/mattermost-server/services/filesstore"
 	"github.com/mattermost/mattermost-server/utils"
@@ -20,7 +21,7 @@ import (
 )
 
 func TestMailConnectionFromConfig(t *testing.T) {
-	cfg, _, _, err := utils.LoadConfig("config.json")
+	cfg, _, _, err := config.LoadConfig("config.json")
 	require.Nil(t, err)
 
 	if conn, err := ConnectToSMTPServer(cfg); err != nil {
@@ -43,7 +44,7 @@ func TestMailConnectionFromConfig(t *testing.T) {
 }
 
 func TestMailConnectionAdvanced(t *testing.T) {
-	cfg, _, _, err := utils.LoadConfig("config.json")
+	cfg, _, _, err := config.LoadConfig("config.json")
 	require.Nil(t, err)
 
 	if conn, err := ConnectToSMTPServerAdvanced(
@@ -93,7 +94,7 @@ func TestMailConnectionAdvanced(t *testing.T) {
 }
 
 func TestSendMailUsingConfig(t *testing.T) {
-	cfg, _, _, err := utils.LoadConfig("config.json")
+	cfg, _, _, err := config.LoadConfig("config.json")
 	require.Nil(t, err)
 	utils.T = utils.GetUserTranslations("en")
 
@@ -135,7 +136,7 @@ func TestSendMailUsingConfig(t *testing.T) {
 }
 
 func TestSendMailUsingConfigAdvanced(t *testing.T) {
-	cfg, _, _, err := utils.LoadConfig("config.json")
+	cfg, _, _, err := config.LoadConfig("config.json")
 	require.Nil(t, err)
 	utils.T = utils.GetUserTranslations("en")