Vector: Implement find, find_if, find_first_matching in terms of AK::find*

Problem:
- The implementation of `find` is coupled to the implementation of `Vector`.
- `Vector::find` takes the predicate by value which might be expensive.

Solution:
- Decouple the implementation of `find` from `Vector` by using a
  generic `find` algorithm.
- Change the name of `find` with a predicate to `find_if` so that a
  binding reference can be used and the predicate can be forwarded to
  avoid copies.
- Change all the `find(pred)` call sites to use `find_if`.

Libraries/LibCore/ArgsParser.cpp

@@ -109,7 +109,7 @@ bool ArgsParser::parse(int argc, char** argv, bool exit_on_failure)
             index_of_found_long_option = -1;
         } else {
             // It was a short option, look it up.
-            auto it = m_options.find([c](auto& opt) { return c == opt.short_name; });
+            auto it = m_options.find_if([c](auto& opt) { return c == opt.short_name; });
             ASSERT(!it.is_end());
             found_option = &*it;
         }