[Kernel] make yojson a mandatory dependence

INSTALL.md

Makefile

Makefile.generating

configure.in

doc/userman/user-sources.tex

headers/header_spec.txt

man/frama-c.1

man/frama-c.1.md

nix/default.nix

opam/opam

share/Makefile.config.in

src/kernel_internals/runtime/config.ml.in

src/kernel_internals/runtime/config.mli

...rnel_services/ast_queries/json_compilation_database.ko.ml

src/kernel_services/ast_queries/json_compilation_database.ml

src/kernel_services/plugin_entry_points/kernel.ml

src/kernel_services/plugin_entry_points/kernel.mli