MINOR: Ensure a single version of scala-library is used (#9155)

This patch ensures we use a force resolution strategy for the scala-library dependency.

I've tested this locally and saw a difference in the output.

With the change (using 2.4 and the jackson library 2.10.5):
```
./core/build/dependant-libs-2.12.10/scala-java8-compat_2.12-0.9.0.jar
./core/build/dependant-libs-2.12.10/scala-collection-compat_2.12-2.1.2.jar
./core/build/dependant-libs-2.12.10/scala-reflect-2.12.10.jar
./core/build/dependant-libs-2.12.10/scala-logging_2.12-3.9.2.jar
./core/build/dependant-libs-2.12.10/scala-library-2.12.10.jar
```

Without (using 2.4 and the jackson library 2.10.5):
```
 find . -name 'scala*.jar'
./core/build/dependant-libs-2.12.10/scala-java8-compat_2.12-0.9.0.jar
./core/build/dependant-libs-2.12.10/scala-collection-compat_2.12-2.1.2.jar
./core/build/dependant-libs-2.12.10/scala-reflect-2.12.10.jar
./core/build/dependant-libs-2.12.10/scala-logging_2.12-3.9.2.jar
./core/build/dependant-libs-2.12.10/scala-library-2.12.12.jar
```

Reviewers: Ismael Juma <ismael@juma.me.uk>

build.gradle

@@ -77,6 +77,12 @@ allprojects {
       runtime {
         resolutionStrategy {
           force(
+            // ensure we have a single version of scala jars in the classpath, we enable inlining
+            // in the scala compiler for the `core` module so binary compatibility is only
+            // guaranteed if the exact same version of the scala jars is used for compilation
+            // and at runtime
+            libs.scalaLibrary,
+            libs.scalaReflect,
             // ensures we have a single version of jackson-annotations in the classpath even if
             // some modules only have a transitive reference to an older version
             libs.jacksonAnnotations,