In this commit we instruct the build system to use the unified schema
files instead of collecting the `TUPLE-TREE-YAML` comments.
The fixes to C++ files are necessary because they depend on the order
of the fields in the schema, which was changed.
The `prettier` binary is now assumed to be installed as part of the
system. No need to manually install it and use the `--prettier`
command-line option.
This commit ensures that `target_tuple_tree_generator` can handle being
invoke multiple times on the same target.
This avoids the need to create a dedicated library as a workaround.
Giacomo Vercesi