ci: Remove Nexus jobs/workflows #2473

Job	Run time
Run Cargo Deny (advisories)	24s
Run Cargo Deny (bans licenses sources)	25s
Decide if Helm charts are pushed to the helm repository based on action trigger	2s
Run Cargo Udeps	2m 3s
Run Rustfmt	26s
Run Clippy	31s
Run RustDoc	1m 16s
Run Cargo Tests	45s
Check if committed README is the one we would render from the available parts	27s
Check if committed Helm charts are up to date	42s
All tests passed	2s
Package Charts, Build Docker Image and publish them - ubicloud-standard-8-arm	11m 9s
Package Charts, Build Docker Image and publish them - ubuntu-latest	12m 29s
Build and publish manifest list	33s
Run the OpenShift Preflight check on the published images	20s
	31m 34s

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