Collect errors and throw instead of just logging them

Similar to https://github.com/swagger-api/swagger-parser/issues/1515 and https://github.com/swagger-api/swagger-codegen/issues/10853, we want to be able to call SwaggerCodegen.main programmatically.

But errors are often just logged instead of an exception being thrown, which doesn't work for non-interactive use cases.

We'd very much like to be able to pass in an option that results in messages being collected and then an exception thrown at the end (they can still be logged as well).

We tried to do this by replacing the logger, but that conflicted with Gradle's logger.

I filed this as well as https://github.com/swagger-api/swagger-parser/issues/1515 because https://github.com/swagger-api/swagger-parser/issues/1515 is specifically about the parser's behavior. Here, we are concerned with the parser, and the codegen configs, and the call to mustache, and anything else in the codepath that encounters a problem.

Start at SwaggerCodegen.main and trace the parser, codegen configuration, Mustache, and other components in its execution path that currently log problems. Define how the new option is passed through this path and verify that messages remain loggable while being collected and reported by an exception at the end for programmatic callers.