chore(BUX-351): improve logging when requesting Pulse

[chris-4chain]

Pull Request Checklist

• 📖 I created my PR using provided : CODE_STANDARDS
• 📖 I have read the short Code of Conduct: CODE_OF_CONDUCT
• 🏠 I tested my changes locally.
• ✅ I have provided tests for my changes.
• 📝 I have used conventional commits.
• 📗 I have updated any related documentation.
• 💾 PR was issued based on the Github or Jira issue.

While doing this task, I discovered that, every time a request to our Pulse service is made, a new http.Client is created. I've change it - so that now, only one http.Client is created during the initialization stage.

From golang documentation:

A Client is an HTTP client. Its zero value (DefaultClient) is a usable client that uses DefaultTransport.

The Client's Transport typically has internal state (cached TCP connections), so Clients should be reused instead of created as needed. Clients are safe for concurrent use by multiple goroutines.

[mergify]

Welcome to our open-source project @chris-4chain! 💘

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (a011827) 53.28% compared to head (97b5bd1) 53.89%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #549      +/-   ##
==========================================
+ Coverage   53.28%   53.89%   +0.60%     
==========================================
  Files         110      110              
  Lines       10854    10853       -1     
==========================================
+ Hits         5784     5849      +65     
+ Misses       4605     4533      -72     
- Partials      465      471       +6     

Flag	Coverage Δ
unittests	53.89% <83.33%> (+0.60%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
chainstate/client.go	65.95% <ø> (ø)
chainstate/client_options.go	74.25% <100.00%> (+3.96%)	⬆️
chainstate/merkle_root.go	83.33% <100.00%> (+83.33%)	⬆️
chainstate/merkle_root_provider.go	66.66% <80.00%> (+66.66%)	⬆️

... and 1 file with indirect coverage changes

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