Normalize remote post site IDs

[crazytonyli]

The site_ID in WP.com rest/1.x API response may be a string or a number. I noticed this issue in testing publishing from the share sheet.

To test:

1. From Xcode, build and run WordPressShareExtension with the Photos app.
2. Share a photo -> tap the WordPress icon -> complete the form to publish the post
3. Wait for the request to complete in the background.
4. Xcode shows a crash at DDLog

[wpmobilebot]

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

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	33112
	Version	PR #25773
	Bundle ID	org.wordpress.alpha
	Commit	3f2865f
	Installation URL	79c5okseb0h4g

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 by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	33112
	Version	PR #25773
	Bundle ID	com.jetpack.alpha
	Commit	3f2865f
	Installation URL	6vtbbo33re0k0

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