all: Remove lib/util package (#9049)

Grab-bag packages are nasty, this cleans it up a little by splitting it
into topical packages sempahore, netutil, stringutil, structutil.

lib/api/api_test.go

@@ -44,8 +44,8 @@ import (
 	"github.com/syncthing/syncthing/lib/sync"
 	"github.com/syncthing/syncthing/lib/tlsutil"
 	"github.com/syncthing/syncthing/lib/ur"
-	"github.com/syncthing/syncthing/lib/util"
 	"github.com/thejerf/suture/v4"
+	"golang.org/x/exp/slices"
 )
 
 var (
@@ -1313,7 +1313,7 @@ func TestBrowse(t *testing.T) {
 
 	for _, tc := range cases {
 		ret := browseFiles(ffs, tc.current)
-		if !util.EqualStrings(ret, tc.returns) {
+		if !slices.Equal(ret, tc.returns) {
 			t.Errorf("browseFiles(%q) => %q, expected %q", tc.current, ret, tc.returns)
 		}
 	}

lib/api/confighandler.go

@@ -15,7 +15,7 @@ import (
 
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/protocol"
-	"github.com/syncthing/syncthing/lib/util"
+	"github.com/syncthing/syncthing/lib/structutil"
 )
 
 type configMuxBuilder struct {
@@ -212,7 +212,7 @@ func (c *configMuxBuilder) registerDefaultFolder(path string) {
 
 	c.HandlerFunc(http.MethodPut, path, func(w http.ResponseWriter, r *http.Request) {
 		var cfg config.FolderConfiguration
-		util.SetDefaults(&cfg)
+		structutil.SetDefaults(&cfg)
 		c.adjustFolder(w, r, cfg, true)
 	})
 
@@ -228,7 +228,7 @@ func (c *configMuxBuilder) registerDefaultDevice(path string) {
 
 	c.HandlerFunc(http.MethodPut, path, func(w http.ResponseWriter, r *http.Request) {
 		var cfg config.DeviceConfiguration
-		util.SetDefaults(&cfg)
+		structutil.SetDefaults(&cfg)
 		c.adjustDevice(w, r, cfg, true)
 	})
 
@@ -266,7 +266,7 @@ func (c *configMuxBuilder) registerOptions(path string) {
 
 	c.HandlerFunc(http.MethodPut, path, func(w http.ResponseWriter, r *http.Request) {
 		var cfg config.OptionsConfiguration
-		util.SetDefaults(&cfg)
+		structutil.SetDefaults(&cfg)
 		c.adjustOptions(w, r, cfg)
 	})
 
@@ -282,7 +282,7 @@ func (c *configMuxBuilder) registerLDAP(path string) {
 
 	c.HandlerFunc(http.MethodPut, path, func(w http.ResponseWriter, r *http.Request) {
 		var cfg config.LDAPConfiguration
-		util.SetDefaults(&cfg)
+		structutil.SetDefaults(&cfg)
 		c.adjustLDAP(w, r, cfg)
 	})
 
@@ -298,7 +298,7 @@ func (c *configMuxBuilder) registerGUI(path string) {
 
 	c.HandlerFunc(http.MethodPut, path, func(w http.ResponseWriter, r *http.Request) {
 		var cfg config.GUIConfiguration
-		util.SetDefaults(&cfg)
+		structutil.SetDefaults(&cfg)
 		c.adjustGUI(w, r, cfg)
 	})