Transitive dependencies can be confusing and hard to deal with when
conflicts arise between them. This change removes transitive
dependencies from elasticsearch, and forces any dependency conflicts to
be resolved manually, instead of automatically by gradle.
closes#14627
Some dependencies must be specified in a couple places in the build.
e.g. randomized runner is specified both in buildSrc (for the gradle
wrapper plugin), as well as in the test-framework.
This change creates buildSrc/versions.properties which acts similar to
the set of shared version properties we used to have in the maven parent
pom.