feat: Add ApiVersion support

[lqiu96]

Generator changes that depends on Google-Api-Java-Client changes in googleapis/google-api-java-client#2462

Example of the generated code:

...
          private static final String API_VERSION = "v1_20230601";
...
          protected List(java.lang.String parent) {
            super(DeltaVExample.this, "GET", REST_PATH, null, com.google.api.services.dev_deltav_pa_sandbox.v1.model.ListPlanetsResponse.class);
            this.parent = com.google.api.client.util.Preconditions.checkNotNull(parent, "Required parameter parent must be specified.");
            if (!getSuppressPatternChecks()) {
              com.google.api.client.util.Preconditions.checkArgument(PARENT_PATTERN.matcher(parent).matches(),
                  "Parameter parent must conform to the pattern " +
                  "^projects/[^/]+/locations/[^/]+$");
            }
            getRequestHeaders().set(API_VERSION_HEADER, API_VERSION);
          }

[lqiu96]

If the ApiVersion header has already been set, do not override with the version. This is possible in two different ways:

1. Using the AbstractRequest's setRequestHeader(): https://github.com/googleapis/google-api-java-client/blob/fbbc37446b2a34b03ca5401bbe9ca038ff087972/google-api-client/src/main/java/com/google/api/client/googleapis/services/AbstractGoogleClientRequest.java#L317-L319
2. From a few handwritten Apiary wrapped libraries (i.e. Storage and Bigquery) as Java-Core provides an option to set a HeaderProvider via ServiceOptions: https://github.com/googleapis/sdk-platform-java/blob/e1e1fb66d95adc08baea71c5a0607c20d5a57a8b/java-core/google-cloud-core/src/main/java/com/google/cloud/ServiceOptions.java#L281-L303

Customers can technically set the X-Goog-Api-Version header themselves via the two options above and this implementation will respect those custom values.

[suztomo]

Nice. Can you record that as source code comment at line 145?

[lqiu96]

Sure, will add a small comment about not override user set value