For methods defined on interfaces (vs concrete methods), the resolution
of the method is necessarily delayed at the run time and can not be
completed at compile time.

The selectorExpr processing has been changed to correctly identify
calls on interface methods which were confused as fields rather
than methods (due to the fact that in a interface definition, methods
are fields of the interface).

Then at runtime, method lookup has been fixed to correctly recurse in
nested valueInterface wrappers and to find embedded interface fields
in case of struct or pointer to structs.

Fixes traefik#1515.

The receiver is already processed at method resolution and in
genFunctionWrapper. Removing redundant processing in call
fixes handling of variadic method, simplifies the code and
makes it faster.

With this commit, it is now possible to run coraza-waf plugin
in traefik.

Co-authored-by: mpl <mathieu.lonjaret@gmail.com>

Co-authored-by: mpl <mathieu.lonjaret@gmail.com>

Co-authored-by: mpl <mathieu.lonjaret@gmail.com>

Co-authored-by: mpl <mathieu.lonjaret@gmail.com>

Co-authored-by: mpl <mathieu.lonjaret@gmail.com>