Enable local variable capture TracePoint when SDK inits

[st0012]

In #1580, only exceptions happen in requests would have its local variables captured for testing purpose. And after more than a week of testing in a real-world Rails app, I didn't see any issue or regression. So this PR enabled the TracePoint globally to make it include exceptions outside of a request (e.g. background jobs).

[codecov-commenter]

Codecov Report

Merging #1589 (6c7f6cc) into master (dde4255) will decrease coverage by 0.00%.
The diff coverage is 85.00%.

❗ Current head 6c7f6cc differs from pull request most recent head a793b4a. Consider uploading reports for the commit a793b4a to get more accurate results

@@            Coverage Diff             @@
##           master    #1589      +/-   ##
==========================================
- Coverage   98.42%   98.41%   -0.01%     
==========================================
  Files         129      129              
  Lines        7218     7245      +27     
==========================================
+ Hits         7104     7130      +26     
- Misses        114      115       +1     

Impacted Files	Coverage Δ
sentry-ruby/lib/sentry-ruby.rb	94.17% <40.00%> (-5.83%)	⬇️
sentry-rails/spec/sentry/rails/activejob_spec.rb	99.25% <100.00%> (+0.02%)	⬆️
sentry-ruby/lib/sentry/rack/capture_exceptions.rb	95.00% <100.00%> (+8.72%)	⬆️
...y-ruby/spec/sentry/rack/capture_exceptions_spec.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry_spec.rb	99.74% <100.00%> (+0.01%)	⬆️

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