When plugins DSL is used, there is no need to
manually generate typesafe accessors for extensions and
conventions (by running `./gradlew kotlinDslAccessorsSnapshot`).
See the previous commit for information on the kotlin-reflect vs
kotlin-reflect-api distinction.
Add kotlin-reflect as an explicit runtime dependency of most of the test
configurations because even though they all depend on tests-common, the
runtime dependency on kotlin-reflect is not exported from tests-common
to other modules because the projectTests dependency is not transitive.
Alexey Tsvetkov