Add pullPolicy option for image building

This commit adds a pullPolicy option to the configuration of the Maven
plugin spring-boot:build-image goal and the Gradle plugin bootBuildImage
task. The new option gives users control over pulling the builder image
and run image from a remote image registry to the local Docker daemon.

See gh-22736

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImageTests.java

@@ -27,6 +27,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import org.springframework.boot.buildpack.platform.build.BuildRequest;
+import org.springframework.boot.buildpack.platform.build.PullPolicy;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -194,4 +195,15 @@ class BootBuildImageTests {
 		assertThat(this.buildImage.createRequest().getRunImage().getName()).isEqualTo("test/run");
 	}
 
+	@Test
+	void whenUsingDefaultConfigurationThenRequestHasNoPullDisabled() {
+		assertThat(this.buildImage.createRequest().getPullPolicy()).isEqualTo(PullPolicy.ALWAYS);
+	}
+
+	@Test
+	void whenNoPullIsEnabledThenRequestHasNoPullEnabled() {
+		this.buildImage.setPullPolicy(PullPolicy.NEVER);
+		assertThat(this.buildImage.createRequest().getPullPolicy()).isEqualTo(PullPolicy.NEVER);
+	}
+
 }