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>

services/convert/issue_comment.go

@@ -76,6 +76,11 @@ func ToTimelineComment(ctx context.Context, repo *repo_model.Repository, c *issu
 			// so we check for the "|" delimiter and convert new to legacy format on demand
 			c.Content = util.SecToTime(c.Content[1:])
 		}
+
+		if c.Type == issues_model.CommentTypeChangeTimeEstimate {
+			timeSec, _ := util.ToInt64(c.Content)
+			c.Content = util.TimeEstimateString(timeSec)
+		}
 	}
 
 	comment := &api.TimelineComment{

services/forms/user_form_hidden_comments.go

@@ -43,6 +43,7 @@ var hiddenCommentTypeGroups = hiddenCommentTypeGroupsType{
 		/*14*/ issues_model.CommentTypeAddTimeManual,
 		/*15*/ issues_model.CommentTypeCancelTracking,
 		/*26*/ issues_model.CommentTypeDeleteTimeManual,
+		/*38*/ issues_model.CommentTypeChangeTimeEstimate,
 	},
 	"deadline": {
 		/*16*/ issues_model.CommentTypeAddedDeadline,

services/issue/issue.go

@@ -105,6 +105,13 @@ func ChangeTitle(ctx context.Context, issue *issues_model.Issue, doer *user_mode
 	return nil
 }
 
+// ChangeTimeEstimate changes the time estimate of this issue, as the given user.
+func ChangeTimeEstimate(ctx context.Context, issue *issues_model.Issue, doer *user_model.User, timeEstimate int64) (err error) {
+	issue.TimeEstimate = timeEstimate
+
+	return issues_model.ChangeIssueTimeEstimate(ctx, issue, doer, timeEstimate)
+}
+
 // ChangeIssueRef changes the branch of this issue, as the given user.
 func ChangeIssueRef(ctx context.Context, issue *issues_model.Issue, doer *user_model.User, ref string) error {
 	oldRef := issue.Ref