Fix PostgreSQL range tests

The changes in c4044b2 meant the tests would error on a fresh DB.
Unused classes in AMo tests
Merge pull request #13393 from matthewd/fix_pg_range_tests

Fix PostgreSQL range tests on fresh DB

Correcting the name of the table we're creating is self-explanatory.

But we must also move away from the low IDs, because we're not touching the freshly-created primary key sequence; when the time comes, @new_range will be assigned an ID of 1.
Update configuring guide with I18n options regarding available locales

Add information about 'available_locales' and 'enforce_available_locales'
to the configuring guide.

Closes #13202. [ci skip]
Fix asserting the correct exception message in dependencies test

In Minitest, the second argument of assert_raise(s) accepts a string as
the message that should be shown in case of a failure in the assertion
(eg nothing was raised when it should), and not the exception message to
be matched.

To do that we need to save the exception returned from assert_raise(s)
into a local variable and check for the exception message using it.
Prefer assert_raise instead of flunk + rescue to test for exceptions

Change most tests to make use of assert_raise returning the raised
exception rather than relying on a combination of flunk + rescue to
check for exception types/messages.
Show routes defined under assets prefix

Closes #9625
Fix PostgreSQL insert to properly extract table name from multiline string SQL.

Previously, executing an insert SQL in PostgreSQL with a command like this:

    insert into articles(
      number)
    values(
      5152
    )

would not work because the adapter was unable to extract the correct articles table name.
Merge pull request #13395 from kuldeepaggarwal/postgres-table-ref-regex

modified regex for finding table_name from a multiline sql query in postgresql
Prevent creation of instance methods when `instance_reader = false`, Grammar checks, Conditional statements combined
Merge pull request #13401 from akshay-vishnoi/refactor

Prevent creation of instance methods when `instance_reader = false`, Grammar checks, Conditional statements combined
[ci skip] Remove <tt> tag in 4_1_release notes.
Merge pull request #13404 from JuanitoFatas/remove-tt

[ci skip] Remove <tt> tag in 4_1_release notes.
Fix assertions for testing unknown formats using Mime::NullType
Fixed configurable.rb regular expression name check
Merge pull request #13406 from hincupetru/master

Fixed configurable.rb regular expression name check
pass over half of the release notes [ci skip]
couple of tweaks to the release notes [ci skip]