AWS: client credentials provider NPE

从 org.apache.iceberg.aws.AwsClientProperties#credentialsProvider 开始，在调用 PropertyUtil.filterProperties 之前检查 clientCredentialsProviderProperties 的处理。复现没有 refresh endpoint 的自定义 credentials provider 场景，然后验证 AWS 客户端可以创建且不会出现报告中的 NullPointerException，并在相关的 AWS properties 测试中增加覆盖率。

Apache Iceberg version

1.11.0 (latest release)

Query engine

None

Please describe the bug 🐞

As of 1.11.0 (https://github.com/apache/iceberg/pull/15249), AwsClientProperties#credentialsProvider unconditionally does a clientCredentialsProviderProperties.put(VendedCredentialsProvider.URI, refreshCredentialsEndpoint) if "client.credentials-provider" is set; this may result in null being put into the properties map. Other similar code paths check first to make sure the value is not null or empty before putting the value.

This does not play well with custom credentials providers / org.apache.iceberg.aws.AwsClientProperties:

java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:233)
	at java.base/java.util.stream.Collectors.lambda$uniqKeysMapAccumulator$1(Collectors.java:180)
	at java.base/java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)
	at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179)
	at java.base/java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1858)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
	at org.apache.iceberg.util.PropertyUtil.filterProperties(PropertyUtil.java:191)
	at org.apache.iceberg.aws.AwsClientProperties.<init>(AwsClientProperties.java:116)
	at io.deephaven.iceberg.util.DeephavenS3ClientCredentialsProvider.create(DeephavenS3ClientCredentialsProvider.java:29)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.apache.iceberg.common.DynMethods$UnboundMethod.invokeChecked(DynMethods.java:60)
	at org.apache.iceberg.common.DynMethods$UnboundMethod.invoke(DynMethods.java:73)
	at org.apache.iceberg.common.DynMethods$StaticMethod.invoke(DynMethods.java:186)
	at org.apache.iceberg.aws.AwsClientProperties.createCredentialsProvider(AwsClientProperties.java:314)
	at org.apache.iceberg.aws.AwsClientProperties.credentialsProvider(AwsClientProperties.java:296)
	at org.apache.iceberg.aws.AwsClientProperties.credentialsProvider(AwsClientProperties.java:218)
	at org.apache.iceberg.aws.s3.S3FileIOProperties.getCredentialsProvider(S3FileIOProperties.java:996)
	at org.apache.iceberg.aws.s3.S3FileIOProperties.applyCredentialConfigurations(S3FileIOProperties.java:985)
	at org.apache.iceberg.aws.AwsClientFactories$DefaultAwsClientFactory.lambda$s3$0(AwsClientFactories.java:116)
	at software.amazon.awssdk.utils.builder.SdkBuilder.applyMutation(SdkBuilder.java:61)
	at org.apache.iceberg.aws.AwsClientFactories$DefaultAwsClientFactory.s3(AwsClientFactories.java:115)
	at io.deephaven.iceberg.util.DeephavenAwsClientFactory.s3(DeephavenAwsClientFactory.java:49)

I'm unclear the exact semantics of nulls in property maps, and if this should be considered an upstream issue (ie, null should not be put in the map), or a downstream issue (AwsClientProperties should be tolerant of entries that have null values).

Willingness to contribute

• I can contribute a fix for this bug independently
• I would be willing to contribute a fix for this bug with guidance from the Iceberg community
• I cannot contribute a fix for this bug at this time