Make options.hosts case insensitive

[joanlopez]

What?

It updates the Hosts type constructor NewHosts store source keys (i.e. hosts) lowercased, to consider them case insensitive. The internal trie, and the Hosts.Match is already considering them insensitive, as they're treated as lowercase.

Why?

Because otherwise, options.hosts doesn't work well with non-lowercase hosts.

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

Closes #3651

Also related with #3620

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.50%. Comparing base (9ee0188) to head (15cb813).

❗ Current head 15cb813 differs from pull request most recent head fe7a778. Consider uploading reports for the commit fe7a778 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3653      +/-   ##
==========================================
- Coverage   73.58%   73.50%   -0.09%     
==========================================
  Files         277      275       -2     
  Lines       20244    20242       -2     
==========================================
- Hits        14896    14878      -18     
- Misses       4400     4410      +10     
- Partials      948      954       +6     

Flag	Coverage Δ
macos	?
ubuntu	73.50% <100.00%> (-0.01%)	⬇️
windows	?

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