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/admin/user/list.tmpl

@@ -91,9 +91,9 @@
 							<td>{{if .IsRestricted}}{{svg "octicon-check"}}{{else}}{{svg "octicon-x"}}{{end}}</td>
 							<td>{{if index $.UsersTwoFaStatus .ID}}{{svg "octicon-check"}}{{else}}{{svg "octicon-x"}}{{end}}</td>
 							<td>{{.NumRepos}}</td>
-							<td>{{template "shared/datetime/short" (dict "Datetime" .CreatedUnix.FormatLong "Fallback" .CreatedUnix.FormatShort)}}</td>
+							<td>{{DateTime "short" .CreatedUnix.FormatLong .CreatedUnix.FormatShort}}</td>
 							{{if .LastLoginUnix}}
-								<td>{{template "shared/datetime/short" (dict "Datetime" .LastLoginUnix.FormatLong "Fallback" .LastLoginUnix.FormatShort)}}</td>
+								<td>{{DateTime "short" .LastLoginUnix.FormatLong .LastLoginUnix.FormatShort}}</td>
 							{{else}}
 								<td><span>{{$.locale.Tr "admin.users.never_login"}}</span></td>
 							{{end}}