* ps/rust-balloon:
ci: enable Rust for breaking-changes jobs
ci: convert "pedantic" job into full build with breaking changes
BreakingChanges: announce Rust becoming mandatory
varint: reimplement as test balloon for Rust
varint: use explicit width for integers
help: report on whether or not Rust is enabled
Makefile: introduce infrastructure to build internal Rust library
Makefile: reorder sources after includes
meson: add infrastructure to build internal Rust library