phia, gh-1452: struct runtime refactoring
phia, gh-1452: struct runtime refactoring

* avoid using void *ptr unnecessarily
* replace struct runtime with struct sfscheme in a few places
* split sfscheme and siconf

rtsisyk/tarantool,mejedi/tarantool,mejedi/tarantool,mejedi/tarantool,rtsisyk/tarantool,mejedi/tarantool,rtsisyk/tarantool,rtsisyk/tarantool