[BUG] Disable UFCS on function named after variable being initialized with CTAD #864

See #550 (comment):

There is another case that #506 doesn't yet cover (https://cpp2.godbolt.org/z/xj1P9cd66):

type_declaration: @struct type = {
  require: (this) = { }
}
require_fn: type == std::function<void(bool, std::string_view)>;
array2: (inout t: type_declaration) = {
  require: std::optional = t.require();
  _ = require;
}
main: () = { }

main.cpp2:6:38: error: variable 'require' declared with deduced type 'std::optional' cannot appear in its own initializer
    6 |   std::optional require {CPP2_UFCS_0(require, t)};
      |                                      ^
main.cpp2:6:17: error: no viable constructor or deduction guide for deduction of template arguments of 'optional'
    6 |   std::optional require {CPP2_UFCS_0(require, t)};
      |                 ^

This is the same as #550 (comment).
Except that we can't easily identify that CTAD is required.
Maybe a nested requirement such as requires { typename std::optional; } might work to detect it.