Resolve "Fix ZeroSSL configuration"

Closes #1059

See merge request !648

Resolve "Remove Rocketchat"

Closes #1049

See merge request !656

Closes: #1049

Close: #1059

Resolve "Revisit flux dependencies"

Closes #1042

See merge request !653

Resolve "Reduce kustomization healthCheck timeouts"

Closes #1055

See merge request !652

first commit to move everything to its own kustomization, also removes deprecated value from kustomizations

Resolve "Update flux"

Closes #1048

See merge request !634

set timeouts for all Flux kustomizations to 20m instead of the default (which is the same as its interval)

Update dependency kubernetes to v20

See merge request !651

Update Helm release metallb to v2.5.13

See merge request !650

Update Helm release ingress-nginx to v4.0.12

See merge request !649

We need helm 3.7 because some charts we use make use of a helm 3.7 feature
(subchart values).
See #1048 for more
details.

Closes: #1048

TRIGGER_JOBS=enable-monitoring,enable-nextcloud,enable-single-sign-on,enable-wekan,enable-wordpress,enable-zulip