Extract a package's build dependencies from its DESCRIPTION
parse_description_deps.RdCollects Imports, Depends, and LinkingTo, strips version constraints,
and drops base packages and R. Suggests is excluded, matching the scope
pak's local_install_deps() installed. LinkingTo is included explicitly
because uvr's own DESCRIPTION parser drops the root package's LinkingTo,
which would miss compile-time header dependencies (for example
RcppArmadillo).