Small refactoring to ChainBuilderType and some proofs

3 jobs for master in 6 minutes and 18 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #90513
au
coq:8.8

00:02:48

passed #90514
au
coq:8.9

00:02:46

passed #90515
au
coq:dev

00:03:31