Fix checkstyle errors and spotbug issue

Author: zoewangg

build-tools/src/main/java/software/amazon/awssdk/buildtools/findbugs/ToBuilderIsCorrect.java

@@ -376,7 +376,7 @@ private void validateBuilderConstructor(String buildableClassName, JavaClass bui
         }
 
         // Find which fields we modified in those constructors
-        Set<String> builderFieldsForBuilder = new HashSet<>(builderFields.get(builder));
+        Set<String> builderFieldsForBuilder = new HashSet<>(builderFields.getOrDefault(builder, new ArrayList<>()));
         Map<String, List<String>> allConstructors = builderConstructorModifiedFields.get(builder);
 
         allInvokedConstructors.forEach(constructorSignature -> {

http-clients/aws-crt-client/src/main/java/software/amazon/awssdk/http/crt/ConnectionHealthConfiguration.java

@@ -27,7 +27,8 @@
  *
  */
 @SdkPublicApi
-public final class ConnectionHealthConfiguration extends CrtConnectionHealthConfiguration implements ToCopyableBuilder<ConnectionHealthConfiguration.Builder, ConnectionHealthConfiguration> {
+public final class ConnectionHealthConfiguration extends CrtConnectionHealthConfiguration
+    implements ToCopyableBuilder<ConnectionHealthConfiguration.Builder, ConnectionHealthConfiguration> {
 
     private ConnectionHealthConfiguration(DefaultBuilder builder) {
         super(builder);
@@ -47,7 +48,8 @@ public Builder toBuilder() {
      *
      * <p>All implementations of this interface are mutable and not thread safe.</p>
      */
-    public interface Builder extends CrtConnectionHealthConfiguration.Builder, CopyableBuilder<Builder, ConnectionHealthConfiguration> {
+    public interface Builder extends CrtConnectionHealthConfiguration.Builder,
+                                     CopyableBuilder<Builder, ConnectionHealthConfiguration> {
 
         @Override
         Builder minimumThroughputInBps(Long minimumThroughputInBps);
@@ -62,7 +64,8 @@ public interface Builder extends CrtConnectionHealthConfiguration.Builder, Copya
     /**
      * An SDK-internal implementation of {@link Builder}.
      */
-    private static final class DefaultBuilder extends CrtConnectionHealthConfiguration.DefaultBuilder<DefaultBuilder> implements Builder {
+    private static final class DefaultBuilder extends
+                                              CrtConnectionHealthConfiguration.DefaultBuilder<DefaultBuilder> implements Builder {
 
         private DefaultBuilder() {
         }

http-clients/aws-crt-client/src/main/java/software/amazon/awssdk/http/crt/ProxyConfiguration.java

@@ -29,7 +29,8 @@
  * @see AwsCrtAsyncHttpClient.Builder#proxyConfiguration(ProxyConfiguration)
  */
 @SdkPublicApi
-public final class ProxyConfiguration extends CrtProxyConfiguration implements ToCopyableBuilder<ProxyConfiguration.Builder, ProxyConfiguration>  {
+public final class ProxyConfiguration extends CrtProxyConfiguration
+    implements ToCopyableBuilder<ProxyConfiguration.Builder, ProxyConfiguration>  {
 
     private ProxyConfiguration(DefaultBuilder builder) {
         super(builder);

http-clients/aws-crt-client/src/main/java/software/amazon/awssdk/http/crt/internal/AwsCrtConfigurationUtils.java

@@ -18,14 +18,9 @@
 
 import java.time.Duration;
 import software.amazon.awssdk.annotations.SdkInternalApi;
-import software.amazon.awssdk.crt.http.HttpMonitoringOptions;
-import software.amazon.awssdk.crt.http.HttpProxyOptions;
 import software.amazon.awssdk.crt.io.SocketOptions;
 import software.amazon.awssdk.crt.io.TlsCipherPreference;
-import software.amazon.awssdk.crt.io.TlsContext;
 import software.amazon.awssdk.http.crt.AwsCrtAsyncHttpClient;
-import software.amazon.awssdk.http.crt.ConnectionHealthConfiguration;
-import software.amazon.awssdk.http.crt.ProxyConfiguration;
 import software.amazon.awssdk.http.crt.TcpKeepAliveConfiguration;
 import software.amazon.awssdk.utils.Logger;
 import software.amazon.awssdk.utils.NumericUtils;