Deprecate unnecessarily exposed attributes

[st0012]

Although they probably aren't used by anyone, directly removing them can still break some users' apps. So I decide to remove them later in version 5.0.0.

[codecov-commenter]

Codecov Report

Merging #1652 (9f7275b) into master (fdf1771) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1652   +/-   ##
=======================================
  Coverage   98.46%   98.46%           
=======================================
  Files         135      135           
  Lines        7534     7542    +8     
=======================================
+ Hits         7418     7426    +8     
  Misses        116      116           

Impacted Files	Coverage Δ
sentry-ruby/lib/sentry/background_worker.rb	94.59% <100.00%> (+0.15%)	⬆️
sentry-ruby/lib/sentry/client.rb	100.00% <100.00%> (ø)
sentry-ruby/lib/sentry/transaction.rb	100.00% <100.00%> (ø)
sentry-ruby/lib/sentry/transport.rb	98.82% <100.00%> (+0.01%)	⬆️
sentry-ruby/lib/sentry/utils/logging_helper.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry/transaction_spec.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry_spec.rb	99.74% <100.00%> (ø)

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