Flink: Backport: Adds support for SpeculativeExecution for IcebergSink

[rodmeneses]

backport of #13642

Backport came out clean

For reference, this is what I did (showing only for 1.19 for simplicity)

git diff HEAD~1 HEAD flink/v2.0/ |sed "s/v2.0/v1.19/g">/tmp/patch_119
git apply -3 -p1 /tmp/patch_119

Applied patch to 'flink/v1.19/flink/src/main/java/org/apache/iceberg/flink/sink/IcebergSink.java' cleanly.
Applied patch to 'flink/v1.19/flink/src/test/java/org/apache/iceberg/flink/source/TestIcebergSpeculativeExecutionSupport.java' cleanly.

[pvary]

Merged to main.
Thanks for the backport @rodmeneses !