Ability to pass env-variables to UI Extension

[KariNarhi28]

Is your feature request related to a problem? Please describe.
Sometimes there are API Keys or other variables that you need to switch between dev/staging and production.

Currently there is no configuration that would pass variables from Plugin to it's UI.

Not talking about the customField-config that passes customField-related data.

Describe the solution you'd like
A config-field in VendurePlugin-config that would pass the other-than-custom-field-data to UI-extension provided inside that plugin.

Describe alternatives you've considered
Allow creation of separate UI-components for different environments and a config-flag that would set the environment for which the Admin UI is built.

Additional context
Related Discord-thread:
https://discord.com/channels/1100672177260478564/1281528744527528018

[dlhck]

This could be done together with #2903