Changes to the API#

Legacy aggregating headers have been removed.#

Previously, some of the legacy API headers existed _only_ to aggregate #include lines for other installed headers. No guidance was provided regarding which header to include for a given feature. These redundant headers have been removed. Client software relying on #include "gromacs/module.h" will need to be updated with more specific #include "gromacs/module/feature.h" directives.

Issue 4487