Introduce table.equals for comparing tables.
The method respects __eq metamethod, if provided.

Needed-for #5894

@TarantoolBot document
Title: lua: new method table.equals

Document the new lua method table.equals
It compares two tables deeply. For example:
```
tarantool> t1 = {a=3}
---
...

tarantool> t2 = {a=3}
---
...

tarantool> t1 == t2
---
- false
...

tarantool> table.equals(t1, t2)
---
- true
...
```
The method respects the __eq metamethod. When both tables being compared
have the same __eq metamethod, it's used for comparison (just like this
is done in Lua 5.1)