addresses "ArgumentError: comparison of VerySpecialComment with SpecialComment failed" in ActiveRecord::DelegationRelationTest#test_#sort!_delegation_is_deprecated

Without this, some tests here were not actually testing anything.

[ci skip]

(No database connection) sounds not be
able to connect database.

see more #12804

This is a follow up to: 97f0d9a0
This change is also related to: df0edafa

This will make the conditional and to code clear

The log output used to be confusing in situation where type casting has
"unexpected" effects. For example when finding records with a `String`.

BEFORE:

irb(main):002:0> Event.find("im-no-integer")
D, [2013-11-09T11:10:28.998857 #1706] DEBUG -- :   Event Load (4.5ms)  SELECT "events".* FROM "events" WHERE "events"."id" = $1 LIMIT 1  [["id", "im-no-integer"]]

AFTER:

irb(main):002:0> Event.find("im-no-integer")
D, [2013-11-09T11:10:28.998857 #1706] DEBUG -- :   Event Load (4.5ms)  SELECT "events".* FROM "events" WHERE "events"."id" = $1 LIMIT 1  [["id", 0]]

This will avoid the broken window effect in our test suite

We can conditional define the tests depending on the adapter or
connection.

Lets keep the skip for fail tests that need to be fixed.

This saved about 46 array allocations per request on an extremely simple
application.  The delegation happened in the notification subsystem
which is a hotspot, so this should result in even more savings with
larger apps.

Squashed commit of the following:

commit 41eef0d1479526f7de25fd4391d98e61c126d9f5
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Wed Nov 6 16:32:31 2013 -0800

    speed up notifications

commit 586b4a18656f66fb2c518fb8e8fee66a016e8ae6
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Wed Nov 6 16:31:05 2013 -0800

    speed up runtime registry methods

commit b67d074cb4314df9a88438f785868cef77e583d7
Author: Aaron Patterson <aaron.patterson@gmail.com>
Date:   Wed Nov 6 16:28:12 2013 -0800

    change method name and make it public

refs #11561 #12700

This allows to assign both `String` and `Symbol` values to the enum
without having to call `to_sym`, which is a security problem.

Commit 6e4a810f changed the implementation
from class_eval to define_method, but missed the access to the constant
versus the access to the constant name.