fix: corrupted rsources stats captured by processor for dropped jobs

[atzoum]

Description

Using a unique job id instead of a zero (0) value for every dropped job so that stats are captured correctly.

Problem

By using the same (0) job id, in_count was being incremented for all different stat key combinations (job_run_id, task_run_id, source_id & destination_id), but failed_count was being erroneously incremented always for the first stat key, due to a corrupted jobIdsToStatKeyIndex.

Linear Ticket

Resolves PIPE-433

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (2d43a0c) 72.38% compared to head (49b376f) 70.39%.
Report is 1 commits behind head on release/1.15.x.

Additional details and impacted files

@@                Coverage Diff                 @@
##           release/1.15.x    #3999      +/-   ##
==================================================
- Coverage           72.38%   70.39%   -2.00%     
==================================================
  Files                 368      357      -11     
  Lines               55595    53686    -1909     
==================================================
- Hits                40244    37792    -2452     
- Misses              13068    13624     +556     
+ Partials             2283     2270      -13     

Files	Coverage Δ
processor/processor.go	88.31% <100.00%> (-4.14%)	⬇️

... and 47 files with indirect coverage changes

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