[cds-plugin-ui5] Option to only include / exclude apps during server start up

[jbibal-pdc]

Is your feature request related to a problem? Please describe. When using the plugin with a big project, with multiple Fiori / UI5 apps, running the CAP / CDS server becomes very slow as it needs to spawn a server for each of the apps, when there are times that we only want to test and work on a particular app.

Describe the solution you'd like Probably a config wherein we can specify which apps to include or maybe exclude when starting the server.

Describe alternatives you've considered Break down the apps into different projects, which is a hassle since the apps share the same domain models.

Additional context