Fix HTTPTransport's ssl configuration

[st0012]

Transport's configuration allows users to configure ssl options with a Ruby hash:

configuration.transport.ssl = { key: value }

or with specific options:

configuration.transport.ssl_verification = false
configuration.transport.ssl_ca_file = file

But there's a bug that will always override the ssl (Hash) option's verify and ca_file values with specific options' values (usually nil in this case).

This bug seems to exist for years (from sentry-raven era), which makes me wonder if anyone really uses the ssl option 🤔

The PR fixes the issue and adds tests for all transport configuration options.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.49%. Comparing base (b61bc0d) to head (941e514).
⚠️ Report is 680 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1626      +/-   ##
==========================================
- Coverage   98.50%   98.49%   -0.01%     
==========================================
  Files         133      133              
  Lines        7336     7382      +46     
==========================================
+ Hits         7226     7271      +45     
- Misses        110      111       +1     

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[sl0thentr0py]

which makes me wonder if anyone really uses the ssl option

^^

lgtm!