all: use T.TempDir to create temporary test directory (#8280)

This commit replaces `os.MkdirTemp` with `t.TempDir` in tests. The
directory created by `t.TempDir` is automatically removed when the test
and all its subtests complete.

Prior to this commit, temporary directory created using `os.MkdirTemp`
needs to be removed manually by calling `os.RemoveAll`, which is omitted
in some tests. The error handling boilerplate e.g.
	defer func() {
		if err := os.RemoveAll(dir); err != nil {
			t.Fatal(err)
		}
	}
is also tedious, but `t.TempDir` handles this for us nicely.

Reference: https://pkg.go.dev/testing#T.TempDir
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

lib/scanner/walk_test.go

@@ -379,11 +379,7 @@ func TestWalkSymlinkWindows(t *testing.T) {
 
 func TestWalkRootSymlink(t *testing.T) {
 	// Create a folder with a symlink in it
-	tmp, err := os.MkdirTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmp)
+	tmp := t.TempDir()
 	testFs := fs.NewFilesystem(testFsType, tmp)
 
 	link := "link"
@@ -712,11 +708,7 @@ func TestStopWalk(t *testing.T) {
 }
 
 func TestIssue4799(t *testing.T) {
-	tmp, err := os.MkdirTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmp)
+	tmp := t.TempDir()
 
 	fs := fs.NewFilesystem(testFsType, tmp)
 
@@ -774,11 +766,7 @@ func TestRecurseInclude(t *testing.T) {
 }
 
 func TestIssue4841(t *testing.T) {
-	tmp, err := os.MkdirTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmp)
+	tmp := t.TempDir()
 
 	fs := fs.NewFilesystem(testFsType, tmp)