Instead of passing the macro based Predicate to findClient it now
expects a function which can be passed to std::find_if.

Existing code like:
xcb_window_t window; // our test window
Client *c = findClient(WindowMatchPredicated(window));

becomes:
Client *c = findClient([window](const Client *c) {
    return c->window() == window;
});

The advantage is that it is way more flexible and has the logic what
to check for directly with the code and not hidden in the macro
definition.

In addition there is a simplified overload for the very common case of
matching a window id against one of Client's windows. This overloaded
method takes a Predicate and the window id.

Above example becomes:
Client *c = findClient(Predicate::WindowMatch, w);

Existing code is migrated to use the simplified method taking
MatchPredicate and window id. The very few cases where a more complex
condition is tested the lambda function is used. As these are very
local tests only used in one function it's not worthwhile to add further
overloads to the findClient method in Workspace.

With this change all the Predicate macro definitions are removed from
utils.h as they are now completely unused.

REVIEW: 116916