Update helpers lib: add function for k8s charm #1224

Job	Run time
Unit tests	2m 30s
Lint	12s
Check libraries	36s
Build charms / Get workflow version / Get workflow version	5s
Build charms / Collect charms	11s
Build charms / Build mongodb charm \| base #0	1m 53s
Build charms / Build legacy-application charm \| base #0	1m 47s
Build charms / Build application charm \| base #0	1m 24s
charm-integration	9m 59s
ha-integration	50m 15s
relation-integration	17m 47s
legacy-integration	4m 17s
tls-integration	23m 45s
backup-integration	54m 13s
metric-integration	19m 41s
sharding-integration	36m 28s
sharding-relation-integration	12m 57s
	3h 58m 0s

Provide feedback