Pull request ElementsProject/lightning#4357

ci: Switch to Github Actions and remove Travis CI

6223
6224
6225
6226
6230
6231
6232
6235

Range Diff Matrix


6223..6224
6223..6225	6224..6225
6223..6226	6224..6226	6225..6226
6223..6230	6224..6230	6225..6230	6226..6230
6223..6231	6224..6231	6225..6231	6226..6231	6230..6231
6223..6232	6224..6232	6225..6232	6226..6232	6230..6232	6231..6232
6223..6235	6224..6235	6225..6235	6226..6235	6230..6235	6231..6235	6232..6235