Migrate scala/* repos to GitHub Actions

[SethTisue]

we'll still have a one-concurrent-job plan on Travis-CI, so we can still do Scala releases and run a few other jobs

https://app.travis-ci.com/github/scala shows which repos are active

• [x] sbt-scala-module
  • [x] https://github.com/scala/sbt-scala-module/pull/139
  • [x] https://github.com/scala/sbt-scala-module/pull/140
  • [x] https://github.com/scala/sbt-scala-module/releases/tag/v3.0.0
• modules:
  • [x] scala-async: https://github.com/scala/scala-async/pull/274, https://github.com/scala/scala-async/pull/278, https://github.com/scala/scala-async/issues/276
  • [x] scala-parser-combinators: https://github.com/scala/scala-parser-combinators/pull/415, https://github.com/scala/scala-parser-combinators/pull/416, https://github.com/scala/scala-parser-combinators/issues/418
  • [x] scala-parallel-collections: https://github.com/scala/scala-parallel-collections/pull/193, https://github.com/scala/scala-parallel-collections/issues/195
  • [x] scala-java8-compat: https://github.com/scala/scala-java8-compat/pull/242, https://github.com/scala/scala-java8-compat/issues/245
  • [x] scala-xml: https://github.com/scala/scala-xml/pull/564
  • [x] scala-swing: https://github.com/scala/scala-swing/pull/157
  • [x] scala-collection-contrib: https://github.com/scala/scala-collection-contrib/pull/151, https://github.com/scala/scala-collection-contrib/pull/152
  • [x] scala-library-next: https://github.com/scala/scala-library-next/pull/98
  • [x] scala-collection-compat: https://github.com/scala/scala-collection-compat/pull/485 (abandoned), https://github.com/scala/scala-collection-compat/pull/486, https://github.com/scala/scala-collection-compat/pull/487, https://github.com/scala/scala-collection-compat/pull/488
• websites:
  • [x] scala.epfl.ch: Seb says he'll find somebody (https://github.com/scala/scala.epfl.ch/issues/194)
  • [x] scala-lang: https://github.com/scala/scala-lang/pull/1276
  • [x] docs.scala-lang: https://github.com/scala/docs.scala-lang/issues/2176
• other:
  • [ ] scala-rewrites: https://github.com/scala/scala-rewrites/issues/125
• [ ] scala-dist, scala-dist-smoketest, scabot, scala-asm:
  • can we just leave these alone? maybe rotate their secrets?
• [ ] nanotest-strawman: https://github.com/scala/nanotest-strawman/pull/160
• [ ] giter8 templates

[SethTisue]

separate ticket on CLA checking: https://github.com/scala/scala-dev/issues/792

[SethTisue]

Not all checkboxes are checked, but I think we've done enough. We can do any other migrations as needed.