Add health check endpoint code (jsonrpsee based version)

[dmidem]

See: #82

This PR addresses the same issue but is based on Zebra v2.4.2, which uses the jsonrpsee crate instead of the unmaintained jsonrpc crate. Since jsonrpsee does not provide a health_api server builder method, the implementation uses ProxyGetRequestLayer with layer to expose the health check endpoint. The solution follows the health endpoint example from the jsonrpsee repo:
https://github.com/paritytech/jsonrpsee/blob/master/tests/tests/helpers.rs#L290

The branch for this PR is based on the upstream v2.4.2 version rather than main. This was simpler here because a copy of the v2.4.2 branch already exists in our fork, and it is effectively the same as main in terms of zebra-rpc and jsonrpsee usage.

All other code, including the response structure definition and tests, was copied from the arseni-health-endpoint branch.

Finally, ci-basic.yml was temporarily added to the .github/workflows folder to run CI for the PR. This file should be removed if the PR is submitted upstream. The tests pass, but the resulting Zebra node has not yet been built and tested with curl to confirm the health endpoint.

Add health check endpoint via the original RPC server
The endpoint will return this data for any GET request:

curl -s http://127.0.0.1:8232/health

response:

{
  "status": "healthy",
  "version": "1.0.0-beta.41",
  "git_tag": "v1.0.0-rc.1",
  "git_commit": "75397cd59d0bac4b4c1e71187bb8af7494efb8b4",
  "timestamp": "2025-09-02T22:35:14.756599+00:00"
}

[seniakalma]

Looks good to me

[PaulLaux]

Looks good. Added one comment and we can open it for upstream.

Also, for upstream, we need changelog documentation and any other step mentioned it the upstream PR template.

[PaulLaux]

closed in favor of #90