Implement ClassFinder filtering in the embedded plugin

[mcollovati]

Both Maven and Gradle plugins allow restricting the classpath elements available for ClassFinder (see FrontendScannerConfig in Maven plugin and ClasspathFilter in Gradle plugin).

The embedded plugin in the extension should provide a similar functionality.
Ideally, restrictions should be configurable via the application.properties file.

vaadin.build.frontend-scanner-config.enabled=true
vaadin.build.frontend-scanner-config.includeOutputDirectory=false
vaadin.build.frontend-scanner-config.includes=my.app.components:*,my.app:ui
vaadin.build.frontend-scanner-config.excludes=my.app.backend:*,*:business-logic

The above rules should be applied in QuarkusPluginAdapter.buildClasspath()

[tltv]

If really needed, as a workaround, one can disable build-in plugin with vaadin.build.enabled=false property and do filtering in Maven/Gradle plugin like in non-quarkus projects (same way as before embedded plugin was introduced).