[Feature] Remove etcd support from BanyanDB codebase

[hanahmily]

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  • I had searched in the issues and found no similar feature requirement.

• Description
  Remove etcd support from BanyanDB’s codebase, including node discovery, schema repository, and relevant test cases.

• Use case
  We want to simplify BanyanDB architecture and reduce maintenance overhead by removing etcd-related code paths and dependencies.
  Scope includes:

  • Removing etcd-based node discovery implementations and related configurations
  • Removing etcd-backed schema repository logic and related integration points
  • Cleaning up docs/scripts/config options tied to etcd support
  • Updating or removing relevant unit/integration/e2e test cases that rely on etcd

  Expected outcome:

  • BanyanDB no longer depends on etcd at runtime
  • Discovery and schema repository behavior are fully supported by non-etcd implementations
  • CI/testing no longer includes etcd-specific scenarios

• Related issues
  N/A

• Are you willing to submit a pull request to implement this on your own?
  (left unchecked as requested)

• Code of Conduct

  • I agree to follow this project's Code of Conduct