Connection: store persistent blog ID for multi-URL purposes (#34262)

* Store persistent blog ID in the options.
* If the current hostname is an IP address, we generate a URL secret and pass it along with other registration data.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/7038990403

composer.json

@@ -7,7 +7,7 @@
 		"php": ">=7.0",
 		"automattic/jetpack-admin-ui": "^0.3.1",
 		"automattic/jetpack-assets": "^2.0.1",
-		"automattic/jetpack-connection": "^2.0.4-alpha",
+		"automattic/jetpack-connection": "^2.1.0-alpha",
 		"automattic/jetpack-jitm": "^3.0.0",
 		"automattic/jetpack-licensing": "^2.0.1",
 		"automattic/jetpack-plugins-installer": "^0.3.0",