GCP, Azure: ignore null values for optional numeric properties

[waterWang]

Problem

GCPProperties and AzureProperties throw NumberFormatException when optional numeric properties exist in the properties map with null values.

properties.containsKey(...) returns true for null-valued entries, but Integer.parseInt(null) / Long.parseLong(null) raises NumberFormatException: Cannot parse null string.

Changes

• GCPProperties.java: Replaced Integer.parseInt(properties.get(...)) with PropertyUtil.propertyAsNullableInt for GCS_CHANNEL_READ_CHUNK_SIZE and GCS_CHANNEL_WRITE_CHUNK_SIZE. Replaced Long.parseLong(properties.get(...)) with PropertyUtil.propertyAsNullableLong for GCS_OAUTH2_TOKEN_EXPIRES_AT, with a null guard before the new Date(...) call.

• AzureProperties.java: Replaced Integer.parseInt(properties.get(...)) with PropertyUtil.propertyAsNullableInt for ADLS_READ_BLOCK_SIZE. Replaced Long.parseLong(properties.get(...)) with PropertyUtil.propertyAsNullableLong for ADLS_WRITE_BLOCK_SIZE.

• TestGCPProperties.java: Added testNullNumericPropertiesAreIgnored to verify null values are treated as absent.

• TestAzureProperties.java: Added testNullBlockSizesAreIgnored to verify null values are treated as absent.

Fixes #17771

[ebyhr]

We can eliminate the if condition above, right?

[ebyhr]

https://iceberg.apache.org/contribute/#conventions-and-recommendations

Omit the test prefix for newly added test methods.

Suggested change

	public void testNullBlockSizesAreIgnored() {
	public void nullValuesAreIgnored() {

There is no need to include "BlockSizes" in my opinion. We may add new entries in the future.