Allow using localized absolute date times within phrases with place holders and localize issue due date events (#24275)

This refactors the `shared/datetime/short|long|full` templates into a
template helper function, which allows us to render absolute date times
within translatable phrases.

- Follows #23988
- The first attempt was in #24055
- This should help #22664 

Changes:
1. Added the `DateTime` template helper that replaces the
`shared/datetime/short|long|full` templates
2. Used find-and-replace with varying regexes to replace the templates
from step 1 (for example, `\{\{template "shared/datetime/(\S+) \(dict
"Datetime" ([^"]+) "Fallback" ([^\)]+\)?) ?\)?\}\}` -> `{{DateTime "$1
$2 $3}}`)
3. Used the new `DateTime` helper in the issue due date timestamp
rendering

# Before

![image](https://user-images.githubusercontent.com/20454870/233791256-b454c455-aca0-4b76-b300-7866c7bd529e.png)

# After

![image](https://user-images.githubusercontent.com/20454870/233790809-c4913355-2822-4657-bb29-2298deb6d4b3.png)

---------

Signed-off-by: Yarden Shoham <git@yardenshoham.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/shared/datetime/full.tmpl

@@ -1 +0,0 @@
-<relative-time format="datetime" weekday="" year="numeric" month="short" day="numeric" hour="numeric" minute="numeric" second="numeric" datetime="{{.Datetime}}">{{.Fallback}}</relative-time>

templates/shared/datetime/long.tmpl

@@ -1 +0,0 @@
-<relative-time format="datetime" year="numeric" month="long" day="numeric" weekday="" datetime="{{.Datetime}}">{{.Fallback}}</relative-time>

templates/shared/datetime/short.tmpl

@@ -1 +0,0 @@
-<relative-time format="datetime" year="numeric" month="short" day="numeric" weekday="" datetime="{{.Datetime}}">{{.Fallback}}</relative-time>

templates/shared/issuelist.tmpl

@@ -106,7 +106,7 @@
 						<span class="due-date" data-tooltip-content="{{$.locale.Tr "repo.issues.due_date"}}">
 							<span{{if .IsOverdue}} class="overdue"{{end}}>
 								{{svg "octicon-calendar" 14 "gt-mr-2"}}
-								{{template "shared/datetime/short" (dict "Datetime" .DeadlineUnix.FormatDate "Fallback" .DeadlineUnix.FormatShort)}}
+								{{DateTime "short" .DeadlineUnix.FormatDate .DeadlineUnix.FormatShort}}
 							</span>
 						</span>
 					{{end}}