[SDTEST-228] Send auto_injected: true to internal telemetry when auto instrumentation was used

[anmarchenko]

What does this PR do?
Adds a couple of small fixes to auto instrumentation:

• test_session telemetry metric has now auto_injected tag set to true when auto instrumentation was used
• when auto instrumentation is used on JRuby, we print error message and bail out of instrumenting tests

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.50%. Comparing base (7e3bb16) to head (20357b8).

Files with missing lines	Patch %	Lines
lib/datadog/ci/auto_instrument.rb	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
- Coverage   98.52%   98.50%   -0.02%     
==========================================
  Files         298      298              
  Lines       14079    14093      +14     
  Branches      680      682       +2     
==========================================
+ Hits        13871    13883      +12     
- Misses        208      210       +2     

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