fix(spark): return NULL from parse_url for a malformed URL unless ANSI

[ozenyunus35]

Which issue does this PR close?

• Closes [Bug] parse_url raises on a malformed URL when ANSI mode is off, Spark returns NULL #26341.

Rationale for this change

In Spark, parse_url returns NULL for a malformed URL unless ANSI mode is on, and only then raises INVALID_URL. The datafusion-spark version always raised, and didn't look at datafusion.execution.enable_ansi_mode, so with the default (ANSI off) a query that returns NULL in Spark failed here.

What changes are included in this PR?

• ParseUrl::invoke_with_args reads enable_ansi_mode from the config, the same way elt does.
• spark_parse_url turns a parse error into NULL when ANSI mode is off, like try_parse_url does; with ANSI mode on it keeps the current error. Argument count and type errors are not affected.

What is the testing strategy for this PR?

• parse_url.slt: the malformed URL case from the issue now returns NULL by default and still errors with enable_ansi_mode = true, and the same for a URL with an out-of-range port (InvalidPort). Without the change, the two NULL cases fail.
• New unit test test_malformed_url_is_null_unless_ansi checks both modes on a batch with a valid and a malformed URL.
• cargo test -p datafusion-spark --lib url::parse_url, the spark/url sqllogictests and cargo clippy -p datafusion-spark --all-targets -- -D warnings pass.

Are there any user-facing changes?

Yes: with ANSI mode off (the default), parse_url returns NULL for a malformed URL instead of an error, matching Spark.

I used an AI assistant to help draft parts of the code and tests; I reviewed the changes and ran the tests myself.