Unify EventLoop.create (#14661)

src/crystal/system/event_loop.cr

@@ -1,6 +1,16 @@
 abstract class Crystal::EventLoop
   # Creates an event loop instance
-  # def self.create : Crystal::EventLoop
+  def self.create : self
+    {% if flag?(:wasi) %}
+      Crystal::Wasi::EventLoop.new
+    {% elsif flag?(:unix) %}
+      Crystal::LibEvent::EventLoop.new
+    {% elsif flag?(:win32) %}
+      Crystal::IOCP::EventLoop.new
+    {% else %}
+      {% raise "Event loop not supported" %}
+    {% end %}
+  end
 
   @[AlwaysInline]
   def self.current : self

src/crystal/system/unix/event_loop_libevent.cr

@@ -1,12 +1,5 @@
 require "./event_libevent"
 
-# :nodoc:
-abstract class Crystal::EventLoop
-  def self.create
-    Crystal::LibEvent::EventLoop.new
-  end
-end
-
 # :nodoc:
 class Crystal::LibEvent::EventLoop < Crystal::EventLoop
   private getter(event_base) { Crystal::LibEvent::Event::Base.new }

src/crystal/system/wasi/event_loop.cr

@@ -1,10 +1,3 @@
-# :nodoc:
-abstract class Crystal::EventLoop
-  def self.create
-    Crystal::Wasi::EventLoop.new
-  end
-end
-
 # :nodoc:
 class Crystal::Wasi::EventLoop < Crystal::EventLoop
   # Runs the event loop.

src/crystal/system/win32/event_loop_iocp.cr

@@ -1,13 +1,6 @@
 require "c/ioapiset"
 require "crystal/system/print_error"
 
-# :nodoc:
-abstract class Crystal::EventLoop
-  def self.create
-    Crystal::IOCP::EventLoop.new
-  end
-end
-
 # :nodoc:
 class Crystal::IOCP::EventLoop < Crystal::EventLoop
   # This is a list of resume and timeout events managed outside of IOCP.