AI Assistant: Update usage of usePostContent for only when necessary (#42149)

* make url optional on useAutosaveAndRedirect as it is only used by one function

* refactor usePostContent hook to expose isEditedPostEmpty

* refactor uses of usePostContent hook

* fix some deprecation warnings

* changelog

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/13594385339

Upstream-Ref: Automattic/jetpack@e908b00

Author: dhasilva

package.json

@@ -23,7 +23,7 @@
 		"@automattic/jetpack-components": "^0.68.0-alpha",
 		"@automattic/jetpack-connection": "^0.38.0-alpha",
 		"@automattic/jetpack-script-data": "^0.2.1",
-		"@automattic/jetpack-shared-extension-utils": "^0.17.3",
+		"@automattic/jetpack-shared-extension-utils": "^0.17.4-alpha",
 		"@automattic/popup-monitor": "1.0.2",
 		"@automattic/social-previews": "2.1.0-beta.10",
 		"@wordpress/annotations": "3.17.0",