Jetpack Sync: Add key for full sync actions (#40566)

* Added key so it is the same when sending full sync actions

* changelog

* Switch to wp_json_encode instead of (string) since terms will show an array in status

* Use chunks_sent instead of last sent to avoid sending weird strings, espceially for term_relationships

* Using last sent again but with crc32

* Not sending specific key for modules that don't send multiple full sync actions

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/12370091919

Upstream-Ref: Automattic/jetpack@f16ae49

composer.json

@@ -6,7 +6,7 @@
 	"require": {
 		"php": ">=7.2",
 		"automattic/jetpack-connection": "^6.2.1",
-		"automattic/jetpack-sync": "^4.1.1"
+		"automattic/jetpack-sync": "^4.2.0-alpha"
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^1.1.1",