fix: multiple helm chart improvements

[floreks]

Fixes #8048

• cert-manager can be fully skipped now. Set cert-manager.enabled=false and app.ingress.issuer.scope=disabled to fully disable it. Note that secretName with the certificate must still be configured to point to the correct secret with a valid certificate.
• nginx can be fully disabled. Set nginx.enabled=false and app.ingress.enabled=false to fully disable it. Note that you have to provide a custom configuration that matches what we do with ingress otherwise, Dashboard will not work.
• updated default nginx configuration to use ClusterIP nginx service and custom internal-nginx ingress class.
• updated NetworkPolicy config to match correct ingress port names
• updated helm chart versioning to start with alpha. When releasing the helm chart we will remove previous "official" releases without alpha suffixes.

TODO:

• Update documentation to cover new changes and inform users about our default configuration and that our dependencies can be replaced.

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[floreks]

@mlbiam does this cover everything mentioned in #8038 or did I miss anything?

[codecov]

Codecov Report

Merging #8103 (806f600) into master (5d81c6f) will decrease coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #8103      +/-   ##
==========================================
- Coverage   42.20%   42.05%   -0.16%     
==========================================
  Files         219      164      -55     
  Lines       12190    10913    -1277     
  Branches      179        0     -179     
==========================================
- Hits         5145     4589     -556     
+ Misses       6748     6064     -684     
+ Partials      297      260      -37     

[mlbiam]

@floreks i think so, i'll get it running my lab