Create axum_utils and begin VC HTTP API migration

[macladson]

Proposed Changes

• Creates axum_utils which contain common functions and types
• Begins migration of the VC HTTP API from warp to axum using warpdrive
• Migrates both metrics servers to axum

[dapplion]

Does warpdrive mess with SSE in any way? Have you tested them?

[macladson]

Does warpdrive mess with SSE in any way? Have you tested them?

warpdrive has a basic example for SSE: https://github.com/macladson/warpdrive/blob/master/examples/sse.rs

Also if we find issues with it we can always migrate the SSE endpoints first

[eserilev]

For others reviewing:

• warpdrive: a nice lil crate Mac put together to convert req/resp from warp to axum. This allows us to use the existing warp server as a fallback service. When reviewing this PR, you should also review this new crate
• We should have buy-in from the team that this will be a "fast" migration from warp to axum in the validator client. We should not go multiple releases with this fallback mechanism in place in the validator client.
• We might just want to migrate the SSE endpoint in this PR and not deal with the overhead of supporting axum <-> warp SSE functionality
• We should run this on a Hoodi node and ensure were not seeing any degraded performance. Some metrics would be nice
• According to claude we may have missing test coverage for the following endpoints
  GET /lighthouse/ui/health
GET /lighthouse/ui/graffiti
GET /lighthouse/beacon/health
POST /lighthouse/beacon/update
GET /lighthouse/logs
DELETE /lighthouse/keystores

We should add test coverage for those sometime during this migration

[mergify]

This pull request has merge conflicts. Could you please resolve them @macladson? 🙏

[mergify]

This pull request has merge conflicts. Could you please resolve them @macladson? 🙏