kn workflow should skip tests during build unless specified

Build can take an eternity because testcontainers is enabled by default in the generated project.

By default, kn workflow build should skip every test unless specified by the user to run the tests.

Users usually would play around with their project and run the tests with quarkus or mvn CLI.

Additional info:
for some reason, testcontainers is kicking off in the build time, which might be related to the tests. As a workaround, you should export the variable TESTCONTAINERS_RYUK_DISABLED=true to skip this stage.