Rename typedef variables in NEST

[pnbabu]

The typedef variables present in nest_types.h should be renamed to names with an appropriate prefix or suffix.

Currently, NESTML synapse models cannot use a variable named delay to identify the dendritic delay because it conflicts with the NEST typedef of the same name. The typedefs could possibly be renamed with a suffix _t (but is generally not recommended as mentioned here) or with a prefix with nest_. Any suggestions?

[github-actions]

Issue automatically marked stale!

[heplesser]

We consciously decided not to use type-suffixes in NEST code. We will review the use of names such as delay for types.

[clinssen]

Note that it would be a possibility to use namespaces to isolate the typedefs, e.g.

namespace nest_types {
    typedef std::vector< size_t > foobar;
}

void f(nest_types::foobar& x) {
   ...
}