Refactor GitHub workflows and prepare release 0.12.0 #514

Job	Run time
Tests (Python-3.8)	4m 32s
Run Slow or Expensive Tests (e.g. SaaS)?	1s
Tests (Python-3.9)	4m 43s
Tests (Python-3.10)	4m 37s
Checks / Version Check & Build Documentation	50s
Checks / Linting and Type checks (Python-3.8)	1m 6s
Checks / Linting and Type checks (Python-3.9)	1m 11s
Checks / Linting and Type checks (Python-3.10)	1m 9s
Checks / Linting and Type checks (Python-3.11)	1m 8s
Gate 1 - Regular CI	1s
metrics / Generate Status Report	48s
Run Slow or Expensive Tests (e.g. SaaS) if Requested	0s
Gate 2 - Allow Merge	0s
	20m 6s

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