[REQ] Build tool configuration parameter

Is your feature request related to a problem? Please describe.

Projects, which generate code required compilation may generate multiple build tool files.
For example java generator may generate maven and gradle projects. This usually make some mess as only one of those build tools will be used in generated project.

Describe the solution you'd like

Add nullable parameter buildTool in DefaultGenerator which may have default value per generator.

buildTool should be a feature of cli so i can choose between gradle, maven, sbt or any other tool specified in feature to generate only one type of project.

buildTool can be null for generators doesn't require tools, ex. javascript.

config example:

generatorName: jax-rs
inputSpec: openapi.yaml
outputDir: resteasy-project
library: resteasy
buildTool: gradle

The request names DefaultGenerator and the CLI feature/configuration path as entry points; start by tracing how generator-specific defaults and CLI parameters are handled. Define how gradle, maven, sbt, or a null value select generated build files, including the Java and JavaScript cases. Done means a configuration can select one build tool without generating the others.