Switch from Travis to Github Actions CI (#2041)

* Fix .run_formal_checks for Github Actions instead of Travis
* Remove .run_chisel_tests

Because we publish SNAPSHOTs on every merge to master, the Chisel repo
checks against master of FIRRTL regularly

* Only run unidoc for Scala 2.12

Under Travis we ran for 2.11, 2.12, and 2.13, but it doesn't work when
using ++2.<major>.<minor> when major != to 2.12. It seems if we want to
run all 3, we have to run as `sbt +unidoc`. It's not clear how much
benefit we get from building on the other versions, so stick with 2.12
for now.

* Generate .mergify.yml with script in chisel-repo-tools

Generated with config:

conditions:
  - status-success=all tests passed
branches:
  - 1.2.x
  - 1.3.x
  - 1.4.x

1 files changed, 0 insertions, 20 deletions

diff --git a/.run_chisel_tests.sh b/.run_chisel_tests.sh
deleted file mode 100644
index dbec894e..00000000
--- a/.run_chisel_tests.sh
+++ /dev/null
@@ -1,20 +0,0 @@
-# SPDX-License-Identifier: Apache-2.0
-set -e
-
-# Use appropriate branches.
-# Each stable branch of FIRRTL should have a fixed value for these branches.
-CHISEL_BRANCH="master"
-TREADLE_BRANCH="master"
-
-# Skip chisel tests if the commit message says to
-# Replace ... with .. in TRAVIS_COMMIT_RANGE, see https://github.com/travis-ci/travis-ci/issues/4596
-if git log --format=%B --no-merges ${TRAVIS_COMMIT_RANGE/.../..} | grep '\[skip chisel tests\]'; then
-  exit 0
-else
-  sbt $SBT_ARGS publishLocal
-  git clone https://github.com/freechipsproject/treadle.git --single-branch -b ${TREADLE_BRANCH} --depth 10
-  (cd treadle && sbt $SBT_ARGS publishLocal)
-  git clone https://github.com/ucb-bar/chisel3.git --single-branch -b ${CHISEL_BRANCH}
-  cd chisel3
-  sbt $SBT_ARGS test
-fi