Previously when converting AS::TimeWithZone to YAML it would be output
as a UTC timestamp. Whilst this preserves the time information accurately
it loses the timezone information. This commit changes that so that it is
saved along with the time information. It also provides nicer encoding of
AS::TimeZone instances themselves which previously embedded all of the
data from the TZInfo records.

Fixes #9183.

Make strptime behave more like parse when components are missing and
share behavior between the two methods.

This makes it easier to parse user-inputted times as from a given time zone.

Currently `Rails.cache.clear` raises Errno::ENOENT if it's run just
after cloning a new Rails project. It should succeed without removing
files or directories.

At present, if you skip a callback that hasn't been defined,
activesupport callbacks silently does nothing. However, it's easy to
mistype the name of a callback and mistakenly think that it's being
skipped, when it is not.

This problem even exists in the current test suite.
CallbacksTest::SkipCallbacksTest#test_skip_person attempts to skip
callbacks that were never set up.

This PR changes `skip_callback` to raise an `ArgumentError` if the
specified callback cannot be found.

This reverts commit 9420de59.

Reason: Turns out we want to keep this method.

We are promoting too much a feature that will not be widler used.
So for now lets keep just the ArrayInquirer constructor.

Wrapping an array in an `ArrayInquirer` gives a friendlier way to check its
string-like contents. For example, `request.variant` returns an `ArrayInquirer`
object. To check a request's variants, you can call:

    request.variant.phone?
    request.variant.any?(:phone, :tablet)

...instead of:

    request.variant.include?(:phone)
    request.variant.any? { |v| v.in?([:phone, :tablet]) }

`Array#inquiry` is a shortcut for wrapping the receiving array in an
`ArrayInquirer`:

    pets = [:cat, :dog]
    pets.cat?    # => true
    pets.ferret? # => false
    pets.any?(:cat, :ferret} # => true

…as discussed #19413

Thanks @fbernier for suggestion! <3
At this moment we can use Module#prepend in all all cases
except of Range because of the bug [1] in MRI 2.2
[1] https://bugs.ruby-lang.org/issues/10847

Skip the `:race_condition_ttl` branch if the option is 0 or nil. This fixes an issue with the redis cache, where this code will sometimes throw an error out of SETEX when passing 0 as the `expires_at`.

Reverting this as it's not the implementation that we would like it to be.
This is being used inside of ActiveSUpport::TimeZone[] and it's unaware
of the context in which to find the timezone period so the timezone found
changes depending on whether DST is in effect for the current period.
This means that `'2001-01-01'.in_time_zone(-9)` changes from winter/summer
even though it's the same date that we're trying to convert.

Since finding timezones by numeric offsets is a bit hit and miss we should
introduce a new API for finding them which supplies the date context in
which we want to search and we should probably also deprecate the finding
of timezones via the [] method, though this needs further discussion.

This reverts commit 2cc2fa36.

Closes #19227.

This reverts commit 2f52f969.

Conflicts:
	actionmailer/test/abstract_unit.rb
	actionview/test/abstract_unit.rb
	activemodel/test/cases/helper.rb
	activerecord/test/cases/helper.rb
	activesupport/test/abstract_unit.rb
	railties/test/abstract_unit.rb

When given a specific offset, use the first result found where the
total current offset (including any periodic deviations such as DST)
from UTC is equal.

[Robin Dupret + Rafael Mendonça França]

[egilburg]

Fixes #19070.

Adds `read_multi` instrumentation formatted as:

Caches multi read:
- views/david/2/4184ab71db6849621a4d8820fcd2c0ad
- views/david/2/4184ab71db6849621a4d8820fcd2c0ad
- views/david/3/4184ab71db6849621a4d8820fcd2c0ad
- views/david/3/4184ab71db6849621a4d8820fcd2c0ad

`coder.represent_scalar` means something along the lines of "Here is a quoted
string, you can just add it to the output", which is not the case here. It only
works for simple strings that can appear unquoted in YAML, but causes problems
for e.g. primitive-like strings ("1", "true").

`coder.represent_object` on the other hand, means that "This is the Ruby-object
representation for this thing suitable for use in YAML dumping", which is what
we want here.

Before:

   YAML.load ActiveSupport::SafeBuffer.new("Hello").to_yaml  # => "Hello"
   YAML.load ActiveSupport::SafeBuffer.new("true").to_yaml   # => true
   YAML.load ActiveSupport::SafeBuffer.new("false").to_yaml  # => false
   YAML.load ActiveSupport::SafeBuffer.new("1").to_yaml      # => 1
   YAML.load ActiveSupport::SafeBuffer.new("1.1").to_yaml    # => 1.1

 After:

   YAML.load ActiveSupport::SafeBuffer.new("Hello").to_yaml  # => "Hello"
   YAML.load ActiveSupport::SafeBuffer.new("true").to_yaml   # => "true"
   YAML.load ActiveSupport::SafeBuffer.new("false").to_yaml  # => "false"
   YAML.load ActiveSupport::SafeBuffer.new("1").to_yaml      # => "1"
   YAML.load ActiveSupport::SafeBuffer.new("1.1").to_yaml    # => "1.1"

If we ever want Ruby to behave more like PHP or JavaScript though, this is an
excellent trick to use ;)

This caused a performance regression since we were decided to do the nil
check in run time not in the load time.

See https://github.com/rails/rails/pull/15187#issuecomment-71760058

Conflicts:
	activesupport/lib/active_support/values/time_zone.rb