Use mechanism to track crashed sessions for unhandled exceptions

[sl0thentr0py]

part of #1743

[codecov]

Codecov Report

Merging #2281 (32b5e14) into neel/mechanism (5eb6f42) will increase coverage by 0.03%.
The diff coverage is 100.00%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           neel/mechanism    #2281      +/-   ##
==================================================
+ Coverage           97.62%   97.65%   +0.03%     
==================================================
  Files                 113      103      -10     
  Lines                4170     3843     -327     
==================================================
- Hits                 4071     3753     -318     
+ Misses                 99       90       -9     

Components	Coverage Δ
sentry-ruby	98.28% <100.00%> (-0.04%)	⬇️
sentry-rails	95.22% <ø> (ø)
sentry-sidekiq	∅ <ø> (∅)
sentry-resque	90.76% <ø> (ø)
sentry-delayed_job	95.60% <ø> (ø)
sentry-opentelemetry	∅ <ø> (∅)

Files	Coverage Δ
sentry-ruby/lib/sentry/hub.rb	99.38% <100.00%> (ø)
sentry-ruby/lib/sentry/session.rb	100.00% <100.00%> (ø)

... and 13 files with indirect coverage changes