feat: implement parse_url

[parthchandra]

Which issue does this PR close?

Part of #4150.

Rationale for this change

parse_url is a commonly used Spark SQL function that currently falls back to the JVM. Adding native support lets Comet accelerate queries that use it. The native implementation in DataFusion already exists (datafusion-spark crate); this PR wires the Spark expression through the Comet serde layer to the native
UDFs.

Because the native implementation has known divergences from Spark on certain edge cases (percent-encoding in QUERY values, FILE part for path-less URLs — tracked in apache/datafusion#21943), the expression is marked Incompatible and gated behind
spark.comet.expression.ParseUrl.allowIncompatible=true.

Note: #4152 implemented parse_url but was closed in favor of #4231 which did not implement parse_url

What changes are included in this PR?

• Serde handler (url.scala): New CometParseUrl handler that maps ParseUrl to either parse_url or try_parse_url native UDF depending on failOnError (ANSI mode).
• Spark 4.x shim (both spark-4.0 and spark-4.1 CometExprShim.scala): Handle Invoke(Literal(ParseUrlEvaluator), "evaluate", args) — the rewritten form of ParseUrl in Spark 4.x — by reconstructing a ParseUrl node and re-dispatching through the serde framework. Propagates EXTENSION_INFO tags so fallback reasons
  are reported correctly.
• UDF registration (jni_api.rs): Register SparkParseUrl and SparkTryParseUrl UDFs with the DataFusion session context.
• Expression map (QueryPlanSerde.scala): Add urlExpressions map and include it in the combined expression lookup.
• Doc generation (GenerateDocs.scala): Add "url" category so compatibility docs are auto-generated.
• Compatibility docs (url.md): Template for auto-generated URL expression compatibility table.

How are these changes tested?

Three new SQL test files covering different configurations:

• parse_url.sql — Default config (allowIncompatible=false): verifies the expression falls back with the expected incompatibility reason.
• parse_url_enabled.sql — With allowIncompatible=true: exercises all URL parts (HOST, PATH, QUERY, PROTOCOL, REF, AUTHORITY, USERINFO, FILE), literal and column-valued arguments, NULL handling, malformed URLs, column-valued part keys, and known edge cases (two tests marked ignore for documented divergences).
• parse_url_ansi.sql — ANSI mode (failOnError=true): verifies the parse_url (non-try) native path works for valid URLs.

All tests pass on both Spark 4.0 and Spark 4.1 profiles.