Expose fiber id for Rust

At the moment we have to use Lua to get fiber id (and it is very painful according to the flame graph)

pub fn fiber_id() -> u64 {
    let lua = tarantool::lua_state();
    lua.eval("return require('fiber').id()").unwrap()
}

mentioned in issue #30 (closed)

See also #30 (closed), we should probably export also functions to set/get fiber name and get csw

assigned to @gmoshkin

See https://github.com/tarantool/tarantool/pull/9238

Done in !128 (merged)

closed

mentioned in issue picodata/picodata/sbroad#541