This will allow us to use the matched params as part of the vars later.

This adds `uri_param_<name>` allowing vars and filters access to the parameters of a uri.
By doing this we are able to improve validation of routes to specific params.

As match_route_opts now handles both the opts and params we can set the matched information in match_route_opts to avoid some duplicate code.

It seems `setmetatable` is very slow and was destroying the benchmark. For this reason we now use `clone_tab` and add the uri matches.

No need to capture this data.

There is no need to return `nil` as this is the default so let's avoid adding it.

[table.clone](https://github.com/openresty/luajit2#tableclone) won't copy metamethods.
So in order to avoid any issues the [__index](https://www.lua.org/pil/13.4.1.html) metamethod is added to the new ops_vars.