Remove unused `get_some_initial_peers` RPC

[glyh]

Summary

The get_some_initial_peers RPC appears to be dead code and should be removed unless there is an out-of-tree caller that still depends on it.

Background

While tracing bootstrap peer selection, I found that seed peer choice is driven by configured initial_peers, optional seed_peer_list_url, and libp2p/DHT bootstrap setup.

Relevant paths:

• src/app/cli/src/cli_entrypoint/mina_cli_entrypoint.ml builds initial_peers
• src/lib/gossip_net/libp2p.ml merges seed peers and adds them to libp2p
• src/app/libp2p_helper/src/codanet.go passes seeds into dht.BootstrapPeers(...)

The RPC itself is still defined:

• src/lib/mina_networking/rpcs.ml defines Get_some_initial_peers
• src/lib/mina_networking/mina_networking.ml exposes the RPC through the networking layer

However, I could not find a production call site for this RPC. Search results only show:

• the RPC definition/registration
• metrics
• fake/test network hooks

Why remove it

• Reduces dead code in the networking surface area
• Removes an apparently unused RPC and its associated metrics
• Simplifies reasoning about how bootstrap peer discovery actually works

Proposed work

• Remove Get_some_initial_peers from src/lib/mina_networking/rpcs.ml
• Remove any corresponding exposure from src/lib/mina_networking/mina_networking.mli and related interfaces
• Remove metrics that only exist for this RPC
• Update tests/fakes that still mention it
• Verify there is no external or operational dependency before merging

Acceptance criteria

• get_some_initial_peers RPC is removed from the production networking API
• Build/tests pass after removing references
• No bootstrap/discovery behavior changes for normal node startup
• If an external dependency exists, document it and keep/remove the RPC accordingly

Open question

Is there any out-of-tree consumer, operational tooling, or older node workflow still relying on get_some_initial_peers? If not, we should delete it.