[BREAKING, phylo] one more breaking TimeUnit JSON modification

Also, added tests to make sure (de)serialization is correct
3 jobs for dev-phylo-document-dates-with-hh-mm-ss in 26 minutes and 39 seconds (queued for 6 seconds)
latest
Status Job ID Name Coverage
  Check Lint
passed #18848
check-lint

00:06:22

 
  Compile
passed #18849
compile

00:13:46

 
  Test
passed #18850
test

00:06:31