chore: upgrade charts to Flux v2.7.3 release

[ravilr]

What this PR does / why we need it:

• Upgrades the helm charts to use the Flux2 v2.7.3 patch release.
• Adds a pre-upgrade helm hook job, which runs flux migrate to migrate the Flux Custom Resources to their latest API versions. the hook is disabled by default, can be enabled by value settings crds.migration.enabled to true.

Which issue this PR fixes

Special notes for your reviewer:

• I've tested the pre-upgrade hook job by deploying the chart locally, with --set crds.migration.enabled=true and verified that it renders as expected and successful job completion on multitenancy enabled and privileged disabled setup. the migrate job uses the kustomize-controller serviceaccount, which has cluster-admin clusterrole binded, with chart default values. In case of multitenancy enabled and privileged disabled setup, additional rbac access for get, list and update on CRD resource are granted.

Checklist

• DCO signed
• Chart Version bumped
• helm-docs are updated
• Helm chart is tested
• Update artifacthub.io/changes in Chart.yaml
• Run make reviewable

[ravilr]

@stefanprodan @tamalsaha PTAL. Do you think whether the added pre-upgrade helm hook for flux migrate should be enabled by default ?

[tamalsaha]

Can you please rebase?

[tamalsaha]

• Upgrades the helm charts to use the Flux2 v2.7.3 patch release.
• Adds a pre-upgrade helm hook job, which runs flux migrate to migrate the Flux Custom Resources to their latest API versions. the hook is disabled by default, can be enabled by value settings crds.migration.enabled to true.

Please open separate prs for these.

[ravilr]

Please open separate prs for these.

@tamalsaha #270 is open for adding the pre-upgrade hook. Since most of the files will run into conflict again, i'll rebase this PR for upgrading to flux-v2.7.3, after that new PR is reviewed and merged..

[ravilr]

/close. Superseded by #273 and #270.