consensus/bor/heimdall: add new meter and timer metrics in heimdall client

[manav2401]

This PR adds new timer and meter metrics for the heimdall client for gathering relevant data. For now, it keeps track of duration of each request to heimdall and the success and failure count.

TODOs

• Add additional metrics
• Check and verify on datadog

[codecov-commenter]

Codecov Report

Merging #459 (8e13b0f) into develop (2a92cb1) will decrease coverage by 0.05%.
The diff coverage is 32.00%.

@@             Coverage Diff             @@
##           develop     #459      +/-   ##
===========================================
- Coverage    56.96%   56.90%   -0.06%     
===========================================
  Files          609      610       +1     
  Lines        69978    70000      +22     
===========================================
- Hits         39864    39836      -28     
- Misses       26718    26766      +48     
- Partials      3396     3398       +2     

Impacted Files	Coverage Δ
consensus/bor/heimdall/metrics.go	9.09% <9.09%> (ø)
consensus/bor/heimdall/client.go	49.20% <50.00%> (-0.36%)	⬇️
p2p/discover/v4_udp.go	72.75% <0.00%> (-5.51%)	⬇️
p2p/simulations/mocker.go	30.00% <0.00%> (-4.45%)	⬇️
console/console.go	62.69% <0.00%> (-3.97%)	⬇️
p2p/discover/table.go	82.48% <0.00%> (-3.65%)	⬇️
rlp/typecache.go	89.53% <0.00%> (-2.33%)	⬇️
consensus/ethash/ethash.go	55.34% <0.00%> (-1.15%)	⬇️
p2p/simulations/network.go	57.76% <0.00%> (-0.88%)	⬇️
trie/trie.go	76.47% <0.00%> (-0.74%)	⬇️
... and 11 more

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[Leon-Africa]

DD updates confirmed - clear to go.

[manav2401]

DD updates confirmed - clear to go.

Confirmed on DD. All looks good. Link to the list of metrics for reference. We can proceed with merge. @JekaMas @temaniarpit27

[JekaMas]

Looks good to me!