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

Merging #1626 (941e514) into master (b61bc0d) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            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     

Impacted Files	Coverage Δ
sentry-ruby/lib/sentry/transport/http_transport.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/contexts/with_request_mock.rb	100.00% <100.00%> (ø)
...-ruby/spec/sentry/transport/http_transport_spec.rb	100.00% <100.00%> (ø)
sentry-ruby/lib/sentry/breadcrumb.rb	95.65% <0.00%> (-4.35%)	⬇️

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[sl0thentr0py]

which makes me wonder if anyone really uses the ssl option

^^

lgtm!