fix: don't overwrite existing tolerations

[drmorr0]

Related Links

• fix: apply node selector and tolerations to parent objects #214

Description and Rationale

• add_operation will replace existing fields in a JSON object, which is kindof a footgun, anyways the previous version had a bug lmao 😭

Test Steps

• I made sure the test that I wrote incorrectly is correct

• I certify that this PR does not contain any code that has been generated with GitHub Copilot or any other AI-based code generation tool, in accordance with this project's policies.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.76%. Comparing base (eb8918c) to head (3fd6d75).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sk-driver/src/runner.rs	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #215      +/-   ##
==========================================
+ Coverage   75.75%   75.76%   +0.01%     
==========================================
  Files          58       58              
  Lines        3316     3326      +10     
  Branches      165      167       +2     
==========================================
+ Hits         2512     2520       +8     
- Misses        699      701       +2     
  Partials      105      105              

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