iproto: export IPROTO constants to Lua automatically

Currently, to export IPROTO constants to Lua, we define a translation
table in C manually. As a result, some constants are forgotten and some
are exported with mistakes.

Fortunately, we have a mechanism to generate enums and its stringified
names in compile-time. Let's rewrite iproto constants using such mechanism
and generate translation table automatically.

Closes #8443
Closes #8574
Closes #8577

NO_DOC=bugfix