Split up unit tests in build by suite and use of storage

Ensure that test suites that touch storage (database tests, mostly) are
run by the build individually, so that timeouts apply individually and
hence give these tests (that can be quite slow on CI machines) some more
time to run.

Also, split up client tests along cient and js suite lines, also provide a
meson suite for all tests so tests of the same kind can still be run
together.
4 jobs for mjog/test-split-up in 13 minutes and 23 seconds
latest
Status Job ID Name Coverage
  Build
passed #462881
ubuntu

00:03:31

 
  Test
passed #462882
flatpak

00:09:01

 
  Deploy
passed #462883
review

00:00:50

manual #462884
allowed to fail manual
stop_review