Expose information about the build jobs queue to the user

[kwiatekus]

Description

Make users aware of the simultanous builds limitation:

• Provide status information in case function build waits in queue
• Expose the default value for the configuration in the UI for serverless CR.

Reasons
We are limiting the number of simultaneous builds. (Configurable here). Once a build job waits in queue the user has no information about that.

[kyma-bot]

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