Add reply support to Comments v2

[crazytonyli]

Description

Comments v2 supports moderation but not replies. This PR adds reply support for moderators:

1. Moderators can reply to approved or pending comments. Sending a reply to a pending comment also approves the parent.
2. The composer stores drafts per site, account, and comment, and lets users save or delete unfinished replies.
3. Relevant comment lists refresh when the user returns from the detail screen.

Testing instructions

• Enable Comments v2 and sign in to a self-hosted site with an application password.
• Reply to an approved comment. Return to the list and verify the reply appears.
• Reply to a pending comment. Verify the composer shows the approval note and the parent becomes approved.
• Write a reply, cancel, and save the draft. Reopen the composer and verify the text is restored. Delete the draft and verify it does not return.
• Verify Spam and Trash comments have no Reply button.

[dangermattic]

	2 Warnings
⚠️	View files have been modified, but no screenshot or video is included in the pull request. Consider adding some for clarity.
⚠️	This PR is larger than 500 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by 🚫 Danger

[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	34340
	Version	PR #25957
	Bundle ID	org.wordpress.alpha
	Commit	2824a01
	Installation URL	0brb8r88sil1g

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	34340
	Version	PR #25957
	Bundle ID	com.jetpack.alpha
	Commit	2824a01
	Installation URL	6tdqhmo86r7og

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

[wpmobilebot]

🤖 Build Failure Analysis

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