RS Post Settings: Use device timezone for date picker

[nbradbury]

Description

The RS post settings date/time picker was using UTC for displaying and selecting dates, causing users in non-UTC timezones to see times offset from their local time. This switches to device timezone to match the behavior of the old post settings date picker.

In order to avoid confusion regarding the timezone, I've also updated the displayed date/time to include the timezone, which is something the older picker didn't have.

Testing instructions

Date picker timezone:

1. Set device timezone to something other than UTC (e.g., US Eastern)
2. Open RS post settings for a published post
3. Note the displayed publish date/time

• Verify the date and time are shown in the device's local timezone

4. Tap the date field, select a new date, then select a new time

• Verify the date picker shows the correct local date initially
• Verify the time picker shows the correct local hour/minute initially
• Verify the updated date/time displayed in settings reflects the device timezone

5. Save the post and reopen settings

• Verify the saved date/time is displayed correctly in device timezone

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Android by scanning the QR code below to install the corresponding build.

	App Name	WordPress Android
	Build Type	Debug
	Version	pr22704-4ac2945
	Build Number	1487
	Application ID	org.wordpress.android.prealpha
	Commit	4ac2945
	Installation URL	2jqutvtjrils0

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Android by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Android
	Build Type	Debug
	Version	pr22704-4ac2945
	Build Number	1487
	Application ID	com.jetpack.android.prealpha
	Commit	4ac2945
	Installation URL	02agqns9p6hqo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 37.49%. Comparing base (cc26b8d) to head (4ac2945).
⚠️ Report is 1 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...android/ui/postsrs/screens/PostRsSettingsScreen.kt	0.00%	11 Missing ⚠️
...ress/android/ui/postsrs/PostRsSettingsViewModel.kt	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk   #22704      +/-   ##
==========================================
- Coverage   37.49%   37.49%   -0.01%     
==========================================
  Files        2286     2286              
  Lines      120484   120489       +5     
  Branches    16501    16501              
==========================================
  Hits        45173    45173              
- Misses      71637    71642       +5     
  Partials     3674     3674              

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