Remove unused AV helper fixtures from e10a2531

Several fixtures for helpers are removed. They were introduced in
ActionView by @strzalek but never referenced in any test.
Bust the template digest cache key when details are changed

Since the lookup details will influence which template is resolved, they
need to be included in the cache key -- otherwise two different
templates may erroneously share the same digest value.
Fix: Remove broken link on rails 3 guide

As raised in https://github.com/rails/rails/issues/12300
[ci skip]
Merge pull request #11452 from dasch/dasch/details-in-digestor-cache-key

Bust the template digest cache key when details are changed
Merge pull request #12301 from Gazler/guide_3_0_release_notes_broken_link

Documentation Fix: Remove broken link on rails 3 guide

Closes #12300
Merge pull request #12232 from claudiob/delete-unused-helper-fixtures

Remove unused AV helper fixtures from e10a2531
Removes redundant into text

Looks like a remnant sentence fragment from the 3.2 guide.
[ci skip] Fix a typo in Engines.md.
Merge pull request #12310 from JuanitoFatas/fix-a-typo

[ci skip] Fix a typo in Engines.md.
Merge pull request #12307 from douglascalhoun/patch-1

Removes (redundant?) sentence fragment in intro text
Fix typo. This test isn't executed in even postgresql.
Add back options argument in the ActiveRecord::Base.initialize method

This will make easier to hook protected_attributes gem in our code
without making that gem fragile to change in Rails code base.

Closes #12243
Merge pull request #12311 from kennyj/fix_typo_about_uuid

Fix typo. This test isn't executed even in the postgresql.