csl libs: Upgrade scalatest to scalatest 3.0.0 for sbt build
csl libs: Upgrade scalatest to scalatest 3.0.0 for sbt build

Problem

We want our OSS/internal builds to be on the same scalatest version.

Solution

Bump the version and fix tests and dependencies.

RB_ID=889527
TBR=true

twitter/finatra,twitter/finatra,twitter/finatra