feat: create initial external-proofs ExEx crate

[meyer9]

Fixes #165

[Copilot]

Pull Request Overview

Creates a new ExEx (Execution Extension) crate for external proof handling that processes blocks and tracks state changes to optimize proof generation.

• Introduces a new external-proofs ExEx crate with basic structure and execution loop
• Adds the new crate to the workspace members
• Implements foundational components for tracking committed chains and notifying completion

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
crates/exex/external-proofs/src/lib.rs	Main implementation of the ExternalProofExEx struct with initialization and execution loop
crates/exex/external-proofs/Cargo.toml	Package configuration and dependencies for the external-proofs crate
Cargo.toml	Adds external-proofs crate to workspace members

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[Copilot]

Remove commented-out code. If this is intended as a placeholder for future implementation, consider adding a TODO comment with more specific context about what notification handling will be added.

Suggested change

	// match &notification {
	// _ => {}
	// };
	// TODO: Implement notification handling logic here as needed.

[Copilot]

The Primitives generic parameter is unused in the implementation. Since Node::Provider: StateReader is already constrained in the struct definition, consider removing the unused Primitives parameter or add a comment explaining why it will be needed for future functionality.

Suggested change

	impl<Node, Primitives> ExternalProofExEx<Node>
	where
	Node: FullNodeComponents<Types: NodeTypes<Primitives = Primitives>>,
	Primitives: NodePrimitives,
	impl<Node> ExternalProofExEx<Node>
	where
	Node: FullNodeComponents,
	Node::Provider: StateReader,

[dhyaniarun1993]

Link issues aren't related to the PR itself. Merging the PR.