lua: refactor integration code of EE and CE

Patch made following changes:
- add a CMake function lua_multi_source that unpacks symbol names and
  Lua source paths in passed list and compiles Lua source into *.lua.c
  sources using lua_source() function. Function is needed for embedding
  Lua modules consisting from a number of files to Tarantool EE.
- add using lua_multi_source instead of lua_source for etcd client module.
- remove function prototypes and declarations related to extra features.
  All this code is moved to Tarantool EE source code.

Part of #8620
Follows up https://github.com/tarantool/tarantool-ee/issues/443

NO_CHANGELOG=refactoring
NO_DOC=refactoring
NO_TEST=refactoring