Add support for a Console migrator tool in docs

[JakeSCahill]

This pull request introduces a new Wasm module for migrating Redpanda Console configurations from v2 to v3, along with UI updates to support this new feature. The most important change is the creation of the Wasm module.

Try the tool: https://deploy-preview-269--docs-ui.netlify.app/console-migrator

Here is a test case:

login:
  jwtSecret: "oidc-secret"
  useSecureCookies: true
  oidc:
    enabled: true
    issuerUrl: "https://issuer.example.com"
    realm: "example-realm"       # Unsupported; should be removed.
    directory:
      some: "value"            # Unsupported; should be removed.
    clientId: "client-123"
    clientSecret: "secret-123"

New Wasm module for configuration migration:

• console-config-migrator/main.go: Implemented the main logic for migrating configurations, including functions for handling authentication, Kafka settings, role bindings, and other properties.
• console-config-migrator/go.mod: Added the Go module definition and dependencies required for the Wasm module.

Documentation updates:

• console-config-migrator/README.md: Added documentation for building and using the Wasm module for configuration migration.
• preview-src/console-migrator.adoc: Created a new document for previewing the Redpanda Console migration tool and trying it out.

UI enhancements:

• src/css/ace-editor.css: Added custom styles for the Ace editor used in the migration tool UI.
• src/css/modal.css: Introduced styles for modal dialogs.
• preview-src/index.adoc: Added a link to the new Console migration tool in the documentation index.

These changes will enable users to migrate their Redpanda Console configurations from v2 to v3 directly within their browser, providing a more seamless and user-friendly experience.

[netlify]

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[weeco]

Very cool thanks!