Allow configuring metrics HTTP server on separate endpoint

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #651 into master will increase coverage by 4.27%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #651      +/-   ##
==========================================
+ Coverage   46.42%   50.69%   +4.27%     
==========================================
  Files         398      404       +6     
  Lines       50715    51667     +952     
==========================================
+ Hits        23545    26195    +2650     
+ Misses      25391    23467    -1924     
- Partials     1779     2005     +226     

Impacted Files	Coverage Δ
cmd/cortex/chaincmd.go	0.00% <ø> (ø)
cmd/cortex/main.go	18.69% <ø> (ø)
cmd/utils/flags.go	2.12% <0.00%> (-0.02%)	⬇️
common/bytes.go	20.20% <0.00%> (-16.17%)	⬇️
p2p/discover/lookup.go	95.23% <0.00%> (-1.91%)	⬇️
p2p/simulations/mocker.go	33.63% <0.00%> (-1.82%)	⬇️
p2p/rlpx.go	69.97% <0.00%> (-1.42%)	⬇️
rpc/subscription.go	87.32% <0.00%> (-1.41%)	⬇️
p2p/simulations/network.go	59.92% <0.00%> (-0.72%)	⬇️
p2p/simulations/http.go	69.56% <0.00%> (-0.55%)	⬇️
... and 47 more