chg: dev: Check meson.build formatting in CI

Add a new CI job that checks whether all meson.build files in the
repository are formatted in the exact same way as "muon fmt" would
format them.  This enforces formatting consistency across all
meson.build files in the repository and enables updating their contents
using dedicated tools, e.g. "meson rewrite".

See #5379

Merge branch '5379-check-meson.build-formatting-in-ci' into 'main'

See merge request isc-projects/bind9!10770