Issue time estimate, meaningful time tracking (#23113)

Redesign the time tracker side bar, and add "time estimate" support (in "1d 2m" format)

Closes #23112

---------

Co-authored-by: stuzer05 <stuzer05@gmail.com>
Co-authored-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/util/time_str_test.go

@@ -0,0 +1,55 @@
+// Copyright 2024 Gitea. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTimeStr(t *testing.T) {
+	t.Run("Parse", func(t *testing.T) {
+		// Test TimeEstimateParse
+		tests := []struct {
+			input  string
+			output int64
+			err    bool
+		}{
+			{"1h", 3600, false},
+			{"1m", 60, false},
+			{"1s", 1, false},
+			{"1h 1m 1s", 3600 + 60 + 1, false},
+			{"1d1x", 0, true},
+		}
+		for _, test := range tests {
+			t.Run(test.input, func(t *testing.T) {
+				output, err := TimeEstimateParse(test.input)
+				if test.err {
+					assert.NotNil(t, err)
+				} else {
+					assert.Nil(t, err)
+				}
+				assert.Equal(t, test.output, output)
+			})
+		}
+	})
+	t.Run("String", func(t *testing.T) {
+		tests := []struct {
+			input  int64
+			output string
+		}{
+			{3600, "1h"},
+			{60, "1m"},
+			{1, "1s"},
+			{3600 + 1, "1h 1s"},
+		}
+		for _, test := range tests {
+			t.Run(test.output, func(t *testing.T) {
+				output := TimeEstimateString(test.input)
+				assert.Equal(t, test.output, output)
+			})
+		}
+	})
+}