[Custom Fields] Support for copying key and value

[hichamboushaba]

Closes: #12578

Description

This PR adds two menu entries to the overflow menu to allow copying either the key or the value of the custom field.

Steps to reproduce

1. Make sure an order has at least one custom field.
2. Open the order in the app.
3. Tap on "View custom fields"
4. Add or edit a new custom field.
5. Tap on the overflow menu.

Testing information

Test copying the key and the value

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on big (tablet) and small (phone) in case of UI changes, and no regressions are added.

[wpmobilebot]

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

	App Name	WooCommerce-Wear Android
	Platform	⌚️ Wear OS
	Flavor	Jalapeno
	Build Type	Debug
	Commit	4be88f0
	Direct Download	woocommerce-wear-prototype-build-pr12579-4be88f0.apk

[wpmobilebot]

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

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Commit	4be88f0
	Direct Download	woocommerce-prototype-build-pr12579-4be88f0.apk

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.64%. Comparing base (15dbfa7) to head (4be88f0).
Report is 221 commits behind head on trunk.

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk   #12579   +/-   ##
=========================================
  Coverage     40.63%   40.64%           
- Complexity     5668     5670    +2     
=========================================
  Files          1228     1228           
  Lines         68930    68938    +8     
  Branches       9547     9547           
=========================================
+ Hits          28011    28019    +8     
  Misses        38345    38345           
  Partials       2574     2574           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[hichamboushaba]

These entries will be shown even when the key or value are empty, I thought about hiding them when they are, but I didn't implement it because I think it'll complicate the logic for not much added value, WDYT?

[JorgeMucientes]

Works as expected and code looks good.