Refactor help-center components and add chat history feature

[agrullon95]

Recent Conversations	Support History

Fixes https://github.com/Automattic/dotcom-forge/issues/9275 Display recent conversations and support history. This work is behind feature flag help-center-experience

Proposed Changes

• Check for unread conversations and messages.
• Display recent conversations that lead to support history route
• Display conversations in support history and open conversation on click

Why are these changes being made?

Testing Instructions

• Checkout this PR and build it locally
• Add the ff in the url ?flags=help-center-experience
• Create a conversation and type a message
• Locate the relevant ticket in the support sandbox
• Assign to yourself and reply. This will create an unread message in the conversation
• Checkout how that is rendered
• Test various conditions here, with the read/unread count
• Clicking on a recent conversation should navigate to support-history where all chats are displayed
• Clicking on a chat there should open the conversation and allow you to reply