Eth2 API: node endpoints outline

[0xKiwi]

What type of PR is this?
This PR is the outlines for the Eth2 API endpoints for interacting with the node:

​/eth​/v1​/node​/identity
​/eth​/v1​/node​/peers
​/eth​/v1​/node​/peers​/{peer_id}
​/eth​/v1​/node​/version
​/eth​/v1​/node​/syncing
​/eth​/v1​/node​/health

Part of #7510

[codecov]

Codecov Report

Merging #7522 into master will increase coverage by 0.10%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7522      +/-   ##
==========================================
+ Coverage   60.88%   60.98%   +0.10%     
==========================================
  Files         429      428       -1     
  Lines       30738    30714      -24     
==========================================
+ Hits        18715    18732      +17     
+ Misses       9001     8934      -67     
- Partials     3022     3048      +26