feat(docker): allow setting of workerpool in cloud build

[michalmrazek]

Describe your changes

Workerpool can be set when using GCP Cloud Build

Issue ticket number and link

MLOPS-54

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] If it is a core feature, I have added thorough tests.

[codecov-commenter]

Codecov Report

Base: 72.12% // Head: 72.01% // Decreases project coverage by -0.11% :warning:

Coverage data is based on head (271ec95) compared to base (3dbfa42). Patch coverage: 50.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #47 +/- ## ========================================== - Coverage 72.12% 72.01% -0.12% ========================================== Files 55 55 Lines 2551 2562 +11 ========================================== + Hits 1840 1845 +5 - Misses 711 717 +6 ``` | [Impacted Files](https://codecov.io/gh/avast/wanna-ml/pull/47?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=avast) | Coverage Δ | | |---|---|---| | [src/wanna/core/services/docker.py](https://codecov.io/gh/avast/wanna-ml/pull/47/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=avast#diff-c3JjL3dhbm5hL2NvcmUvc2VydmljZXMvZG9ja2VyLnB5) | `66.66% <41.66%> (-1.62%)` | :arrow_down: | | [src/wanna/core/models/docker.py](https://codecov.io/gh/avast/wanna-ml/pull/47/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=avast#diff-c3JjL3dhbm5hL2NvcmUvbW9kZWxzL2RvY2tlci5weQ==) | `97.91% <100.00%> (+0.09%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=avast). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=avast)

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