[gradle] exclude scala-reflect

[danking]

CHANGELOG: Fixes #13837 in which Hail could break a Spark installation if the Hail JAR appears on the classpath before the Scala JARs.

We and several dependencies of ours are exposing an old version of scala-reflect (rude of us and them). If our JAR appears on the classpath before the scala JARs and the sub-versions of Scala differ, Spark is likely to have incompatible bytecode.

See #13837 .

In this PR, this command,

make shadowJar && \
    jar tf build/libs/hail-all-spark.jar | grep scala/reflect | wc -l && \
    jar tf build/libs/hail-all-spark.jar | grep 'MutableSettings'

prints:

    0

On main (5d7dc2cab7) it prints:

    1417
scala/reflect/internal/settings/MutableSettings$.class
scala/reflect/internal/settings/MutableSettings$SettingValue.class
scala/reflect/internal/settings/MutableSettings.class

---

A bit more details follow for the curious.

./gradlew dependencies shows these packages as depending on scala-reflect:

+--- org.scalanlp:breeze-natives_2.12:1.1
|    +--- org.scala-lang:scala-library:2.12.10 -> 2.12.17
|    +--- org.scalanlp:breeze_2.12:1.1 -> 1.2
|    |    +--- org.scala-lang:scala-library:2.12.10 -> 2.12.17
|    |    +--- org.scalanlp:breeze-macros_2.12:1.2
|    |    |    +--- org.scala-lang:scala-library:2.12.10 -> 2.12.17
|    |    |    \--- org.scala-lang:scala-reflect:2.12.10 -> 2.12.15
...
+--- org.elasticsearch:elasticsearch-spark-30_2.12:8.4.3
|    +--- org.scala-lang:scala-library:2.12.8 -> 2.12.17
|    +--- org.scala-lang:scala-reflect:2.12.8 -> 2.12.15 (*)
|    \--- org.apache.spark:spark-core_2.12:3.2.1 -> 3.3.0
...
|         +--- org.scala-lang:scala-reflect:2.12.15 (*)
...
+--- org.scala-lang:scala-reflect:2.12.15 (*)
...
+--- org.apache.spark:spark-sql_2.12:3.3.0
...
|    +--- org.apache.spark:spark-catalyst_2.12:3.3.0
|    |    +--- org.scala-lang:scala-reflect:2.12.15 (*)

This root (the fourth to last package above):

+--- org.scala-lang:scala-reflect:2.12.15 (*)

is coming from this line in build.gradle:

    shadow 'org.scala-lang:scala-reflect:' + scalaVersion

I think shadow means "needed to compile but do not include in shadow JAR", so I do not know if we can trust ./gradlew dependencies to tell us why any particular class file is in our shadow JAR.

[danking]

bump; I'd like to include this in 0.2.125