[ntp modules] Reload NTP module container on new module enables.

Modifies the NTP module framework to show newly enabled modules, without
requiring the NTP to be refreshed.

This supports Microsoft's conditional module display logic, which allows
Microsoft modules to load after the initial module load.

Because modules already manage their visibility based on their enabled
state [1], this change only ensures they are initialized when first
enabled.

Demo:screencast/cast/NTI0MzgxMDQ1OTE1NjQ4MHxhNjUyODllOS0wNA

Follow up CLs will address:
1. Waiting for the initial Microsoft auth state before loading any modules.
2. Recording metrics on reload (if we decide to add any).

[1]https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/resources/new_tab_page/modules/v2/modules.html;l=19

Change-Id: I9cbe1eafa45e87ae34ce27019b9e4046032790a6
Bug: 386380560, 392707563
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6197389
Reviewed-by: Roman Arora <romanarora@chromium.org>
Reviewed-by: Riley Tatum <rtatum@google.com>
Commit-Queue: Paul Adedeji <pauladedeji@google.com>
Cr-Commit-Position: refs/heads/main@{#1414123}