Specify what is creating a background worker

[llhhaa]

Description

Describe your changes:

When running Rails tasks, I see something "initializing the background worker", e.g.:

> bin/rails c
Initializing the background worker with 5 threads
Loading development environment (Rails 7.0.8.1)
[1] pry(main)>

I thought it might be helpful if this message indicated what it is - Sentry - that is doing this:

> bin/rails c
Initializing the Sentry background worker with 5 threads
Loading development environment (Rails 7.0.8.1)
[1] pry(main)>

#skip-changelog

[codecov]

Codecov Report

Merging #2256 (23de453) into master (478c4cf) will increase coverage by 0.20%.
Report is 4 commits behind head on master.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2256      +/-   ##
==========================================
+ Coverage   97.41%   97.61%   +0.20%     
==========================================
  Files         102      112      +10     
  Lines        3828     4153     +325     
==========================================
+ Hits         3729     4054     +325     
  Misses         99       99              

Components	Coverage Δ
sentry-ruby	98.30% <100.00%> (+0.16%)	⬆️
sentry-rails	95.05% <ø> (ø)
sentry-sidekiq	94.70% <ø> (ø)
sentry-resque	92.30% <ø> (+1.53%)	⬆️
sentry-delayed_job	95.60% <ø> (ø)
sentry-opentelemetry	100.00% <ø> (ø)

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

... and 20 files with indirect coverage changes