Polyglot project to support custom runtime environments

[deyan-r]

Description

Polyglot projects define the runtime environment to be used in polyglot.json platform.runtime parameter.
The value is validated against a list of built-in runtime environments.
Polyglot projects should support custom runtime environments as well.
They should be supported for polyglot packaging, vrealize:push, and installation.

Alternatives

Currently, the runtime environment has to be changed manually for each action after importing it.

Additional Context

This change is only relevant for VRO polyglot projects and does not apply to ABX projects.