Pass -Xsource:3 to scalafix organize-imports action if present

[hugo-vrijswijk]

When using organize-imports on Scala 2 with -Xsource:3 a crash would occur when using as import renaming:

2022.01.28 11:08:13 ERROR /..../ConfigReader.scala:8: error: } expected but identifier found
import pureconfig.{ConfigReader as PureConfigReader, ConfigSource}

This is because Scalafix tries to parse the file as Scala 2. Scalafix has support for -Xsource:3 since scalacenter/scalafix#1409 but it needs to be passed in the scalacOptions. With this fix -Xsource:3 is passed to Scalafix if used, fixing the crash and letting Scalafix properly parse and fix the file.

[tgodzik]

Thanks for fixing this! Let's see if the CI passes, then we should be good to merge!

[hugo-vrijswijk]

Thanks! This has been a minor annoyance since using -Xsource:3 and was a surprisingly easy fix!