feat: add _on_upgrade #825

Job	Run time
PR Agent / Check against ignorelist	4s
PR Region / Check against ignorelist	5s
PR Agent / Quality Checks / Check the CHARMHUB_TOKEN secret	1s
PR Agent / Quality Checks / Inclusive naming / check	4s
PR Agent / Quality Checks / Linting / Lint	13s
PR Agent / Quality Checks / Scenario Tests / Scenario tests	19s
PR Agent / Quality Checks / Static Analysis / Static Analysis of Charm	23s
PR Agent / Quality Checks / Unit Tests / Unit tests	14s
PR Agent / Quality Checks / Static Analysis / Static Analysis of Libs	14s
PR Region / Quality Checks / Check the CHARMHUB_TOKEN secret	1s
PR Region / Quality Checks / Inclusive naming / check	4s
PR Region / Quality Checks / Linting / Lint	12s
PR Region / Quality Checks / Scenario Tests / Scenario tests	16s
PR Region / Quality Checks / Static Analysis / Static Analysis of Libs	17s
PR Region / Quality Checks / Static Analysis / Static Analysis of Charm	19s
PR Region / Quality Checks / Unit Tests / Unit tests	15s
PR Agent / Quality Checks / Check libraries	0s
PR Region / Quality Checks / Check libraries	0s
PR Region / Quality Checks / CodeQL analysis / Analyze (python)	1m 18s
PR Region / Quality Checks / Integration Tests / Integration Tests	10m 47s
PR Agent / Quality Checks / CodeQL analysis / Analyze (python)	1m 16s
PR Agent / Quality Checks / Integration Tests / Integration Tests	11m 44s
	28m 6s

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