[Feature] Allow loading configuration into graph-node on-the-fly

Description

We change the config in graph-node quite a bit. This currently means writing a config file and restarting the container. For enterprise level production services it is expected that we should not need to totally restart things. Injecting new configuration while running is a common practice since years.

For things that run under systemd or similar, sending a SIGHUP to reload configuration is normal way to do things.

For many other services they accept sending configuration updates via API calls.

I would propose that graph-node should accept all configuration updates by API call. The graph-node CLI should understand how to read and write this configuration.

Are you aware of any blockers that must be resolved before implementing this feature? If so, which? Link to any relevant GitHub issues.

No.

Some information to help us out

• Tick this box if you plan on implementing this feature yourself.
• I have searched the issue tracker to make sure this issue is not a duplicate.

Start by examining graph-node's configuration handling, API surface, and CLI entry points; the issue names no specific files or tests. Define the supported configuration updates and how API calls, CLI commands, or SIGHUP-based reloads should behave before implementation, then add coverage for the chosen interface.