Reorganise e2e samples

[jvalkeal]

Before we start to add anything related to new annotation model #637, it'd be good if we move legacy annotation commands and registration based commands in their own inner classes.

For example:

public class RequiredValueCommands {

	private final static String REQUIRED_VALUE = "required-value";
	private final static String ARG1_DESC = "Desc arg1";
	private final static String ARG1_NAME = "arg1";

	@ShellComponent
	public static class RequiredValueCommandsLegacyAnnotation extends BaseE2ECommands {

		@ShellMethod(key = LEGACY_ANNO + REQUIRED_VALUE, group = GROUP)
		public String testRequiredValueLegacyAnnotation(
			@ShellOption(help = ARG1_DESC)
			String arg1
		) {
			return "Hello " + arg1;
		}
	}

	@Component
	public static class RequiredValueCommandsRegistration extends BaseE2ECommands {

		@Bean
		public CommandRegistration testRequiredValueRegistration(CommandRegistration.BuilderSupplier builder) {
			return builder.get()
				.command(REG, REQUIRED_VALUE)
				.group(GROUP)
				.withOption()
					.longNames(ARG1_NAME)
					.description(ARG1_DESC)
					.required()
					.and()
				.withTarget()
					.function(ctx -> {
						String arg1 = ctx.getOptionValue(ARG1_NAME);
						return "Hello " + arg1;
					})
					.and()
				.build();
		}
	}
}

This way when we start to add @Command based commands we can have new inner class as well. Not doing this will cause a rebase hell with maintenance branches.