EWC/Enterprise transition to OpenSource

[arm4b]

StackStorm-ha Helm chart provides an upgrade from StackStorm OSS to EWC/Enterprise version by setting a license in Helm values. Besides of that, there are dedicated set of Enterprise Docker images uploaded to private hub.

As Extreme Networks open-sourced the EWC Enterprise (https://stackstorm.com/2020/05/27/extreme-networks-donates-ewc-to-linux-foundation/), remove the Enterprise upgrade functionality from the chart.
Rework the chart so settings like RBAC/LDAP could be easily adjusted.

This could be done once the Enterprise functionality is integrated into StackStorm.

[arm4b]

As v3.3 comes with no EWC packages anymore, I'll need to remove the Enterprise pipeline from the CI/CD.
This means EWC/Enterprise is dropped from K8s/HA since st2 v3.3 until ST2 Maintainers integrate EWC into StackStorm OSS in the next releases.

[arm4b]

EWC/Enterprise testing was removed from stackstorm-ha in v0.40.0 (#157).
Next step is updating the chart to configure RBAC/LDAP as part of StackStorm OSS without an enterprise flag set.