feat(synth): Update default isBlocking behavior

[amolero-nr]

Updates default isBlocking behavior for continuous automated tests in CLI. Ref: NR-182971

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (f23fd47) 47.61% compared to head (11b5491) 47.83%.

Files	Patch %	Lines
internal/synthetics/command_batch_run.go	67.64%	10 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1538      +/-   ##
==========================================
+ Coverage   47.61%   47.83%   +0.21%     
==========================================
  Files         125      125              
  Lines        7791     7825      +34     
==========================================
+ Hits         3710     3743      +33     
  Misses       3939     3939              
- Partials      142      143       +1     

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