Fix key serialization for mutable struct with struct member

This fixes the serialization of keys for a mutable struct that has
a key member with a struct type that contains non-key members.
The serialization kind was not passed to the nested serialize call,
which resulted in non-key members of the nested type being added to
the key.

Additionally a few entries are added to the reserved name list
in the random IDL generator. This solves some runtime errors in
fuzzer runs (`TypeError: 'list' object is not callable` and
`expected identifier or '(' before 'static'`)

Signed-off-by: Dennis Potman <dennis@zettascale.tech>