WIP: Implement client side rendering

[johnbillion]

This starts us down the path of switching over Query Monitor's output to client-side rendered React components.

This has numerous benefits including:

• Better performance (no need to render a big pile of HTML)
• Allowing for state to be swapped out in order to show data for requests other than the current page load (eg. Ajax, REST API, POSTs before a redirect, and historical requests)
• Panels which can be reused outside of the context of WordPress, eg in loggers or browser extensions
• Data accessible elsewhere in the client, eg in the developer tools panel

There's still lots to do, but the concept has been proven.

See #291.

Progress

• Proof of concept
• Functional
• Quality
• Functionally complete
• Shiny and ready to go

Aims

• Feature parity with all existing panels.
• JSON data payload to hydrate the client-side panels. Remove unnecessary properties as we go.
• Retain support for server-side rendered panels so add-ons for QM and Debug Bar continue to work.
• Partial client-side rendering. The main panel container and its menu tabs will remain server-side rendered for the time being. Individual panel contents will be converted to client-side rendering.
• Retain and continuously improve the existing server-side panel rendering until all client-side panels are complete.
• Publish the UI components as an NPM package
• Remove dependency on jQuery

Considerations

• Bundling for WP backwards compatibility. wp.i18n isn't bundled with WP prior to 5.0.
• Bundling in general. Should React be bundled or should core's be used?
• Using data across components, eg most stuff in the Overview panel
  • Slot & Fill?

Usage

npm install --legacy-peer-deps && npm run watch

Per-panel Tasks

The existing collectors and outputters in QM are very well separated, but nevertheless as each panel is worked on the following actions may need to be made:

• Move logic out of the HTML outputter and into the corresponding collector.
• Move translatable strings out of the collector and into the corresponding HTML outputter and React component.

Panel Progress

• overview
  • Use a slot that other components can fill with their data
• admin
• assets_scripts
• assets_styles
• block_editor
• cache
• caps
• conditionals
• db_callers
• db_components
• db_dupes
• db_queries
• doing_it_wrong
• environment
• headers
• hooks
• http
• languages
• logger
• multisite
• php_errors
• raw_request
• request
• theme
• timing
• transients
• Hooks in Use panels
• Settings panel

UI Component Progress

• Toggles
• Filter dropdowns
• Filter links
• Table sorters
• Clickable stack traces
• Table footers

Nope

The following panels will remain server-side rendered:

• debug_bar

[jordantrizz]

Just wondering if this is functional yet?