docs: update plugins page to match current Nethermind API

[smartprogrammer93]

Summary

Updates the plugins documentation to reflect the current state of the Nethermind codebase.

Changes

• Removed references to deleted interfaces: \IInitializationPlugin\ and \ISynchronizationPlugin\ no longer exist in the codebase
• Added \Enabled\ property to all plugin examples (now a required member of \INethermindPlugin)
• Removed boilerplate stubs (\DisposeAsync, empty \InitNetworkProtocol, etc.) — the interface now provides default implementations
• New section: Dependency injection and modules — documents the \Module\ property, \IStep\ interface, \AddStep(), and \RunnerStepDependencies\ attribute (replaces the old \IInitializationPlugin\ pattern)
• Updated Configuration section to show Autofac constructor injection (the modern pattern used by all built-in plugins)
• Added \INethermindPlugin\ reference table documenting all interface members including \MustInitialize\ and \Module\
• Updated log output examples to match current \PluginLoader\ format
• Updated JSON-RPC handler sample with the same fixes

[Copilot]

Pull request overview

Updates the Nethermind plugin developer documentation to match the current plugin API, especially around required INethermindPlugin members, default interface implementations, and the modern DI/module-based initialization pattern.

Changes:

• Updates plugin samples to include the required Enabled property and removes obsolete boilerplate method stubs.
• Refreshes configuration guidance to show Autofac constructor injection and explains Enabled evaluation timing.
• Adds documentation for DI modules and initialization steps, plus an INethermindPlugin member reference table and updated log output examples.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/developers/plugins/samples/json-rpc-handler.md	Updates the JSON-RPC plugin sample to match the current INethermindPlugin surface (adds Enabled, removes unnecessary stubs).
docs/developers/plugins/plugins.md	Refreshes core plugin docs: required members, updated logs, Autofac-based config injection, new DI/modules + steps section, and an INethermindPlugin reference table.

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[Copilot]

The text says this example "registers a custom service and an initialization step", but the code only registers an initialization step via builder.AddStep(typeof(DemoStep));. This is misleading—either add a service registration in the snippet or adjust the description to mention only steps.

Suggested change

	Here is an example of a plugin that registers a custom service and an initialization step:
	Here is an example of a plugin that registers an initialization step:

[Copilot]

The IStep link text points to a file named IEthereumRunnerStep.cs, which reads as a mismatch and makes it hard to confirm the correct interface. Consider updating the URL to the actual IStep definition (or adjusting the link text) so readers land on the right symbol.

Suggested change

	Initialization steps allow plugins to hook into Nethermind's startup sequence. Each step implements the [`IStep`](https://github.com/NethermindEth/nethermind/blob/master/src/Nethermind/Nethermind.Api/Steps/IEthereumRunnerStep.cs) interface and is resolved through Autofac, so its dependencies are injected automatically via the constructor:
	Initialization steps allow plugins to hook into Nethermind's startup sequence. Each step implements the [`IStep`](https://github.com/NethermindEth/nethermind/blob/master/src/Nethermind/Nethermind.Api/Steps/IStep.cs) interface and is resolved through Autofac, so its dependencies are injected automatically via the constructor:

[LukaszRozmej]

We should rename IEthereumRunnerStep.cs to just IStep.cs

[smartprogrammer93]

You mean in code, not in docs, right?