Rework Jenkins scripts

[tszczyp]

FEAT: Drop Jenkins extended API/groovy for external Python/Bash scripts and use basic Jenkins syntax/functionality

Rationale

Complicated extended Jenkins API written in groovy may cause issues for new users. Changing CI/CD tool may need logic reimplementation.

Description

Jenkins Groovy file should be removed and reworked into Python/Bash scripts. Pipelines should use basic Jenkins methods and syntax.

[lukaszstolarczuk]

for longer discussion (and more details) see review issues in: #1