tarantool/checks [1] is a lua module (distributed as a separate rock)
for function input validation. After this patch, it will a part of
the tarantool binary.

1. https://github.com/tarantool/checks

Closes #7726
Needed for #7725

@TarantoolBot document
Title: embedded checks

Now tarantool has checks module on its board. checks is a lua module
previously distributed as a separate rock which is widely used by
many other tarantool lua modules (like cartridge, metrics and crud) and
tarantool applications. checks has its own repo with README covering its
API usage: https://github.com/tarantool/checks/blob/master/README.md .