[GH-3095] Exclude the entire Scala toolchain from shaded jars

[james-willis]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• Yes, and the PR name follows the format [GH-XXX] my subject. Closes Shaded jars should exclude the entire Scala toolchain (org.scala-lang:*), not just scala-library #3095

What changes were proposed in this PR?

Change the shade-plugin exclude in spark-shaded, flink-shaded, and snowflake from org.scala-lang:scala-library to org.scala-lang:*, so scala-reflect/scala-compiler can never be bundled unrelocated into the fat jars and shadow the runtime's Scala toolchain. See #3095 for details. The groupId match is exact, so org.scala-lang.modules:scala-collection-compat stays bundled.

How was this patch tested?

Verified on a downstream build hit by this that the shaded jar goes from containing an unrelocated scala-reflect 2.13.8 to zero scala/reflect/ or scala/tools/ entries, with scala/collection/compat/ still bundled.

Did this PR include necessary documentation updates?

• No, this PR does not affect any public API so no need to change the documentation.