Replace deprecated `memcache-client` gem with `dalli` in ActiveSupport::Cache::MemCacheStore

memcache-client was deprecated in favour of dalli in 2010.

Fix merge error when Equality LHS is non-attribute

Update to activerecord-deprecated_finders on generator

Checking respond_to? incurs overhead, and most of the time when
assigning attributes it will return true. So just handle the
NoMethodError instead.

any? will check that each item in the array is truthy, as opposed to
!empty? which will simply check that the array has length. For an empty
array, !empty? still seems to be faster than any?

Rather than doing it every time an instance is instantiated.

Those z's were hard to type.

deep_dup is slow. we only need to dup the values, so just do that
directly.

Fixes #7374

Fix occasional microsecond conversion inaccuracy

This is at best a band-aid for a more proper fix, since it won't truly
handle the removal of the previous equality condition of these other
nodes. I'm planning to put in some work on ARel toward supporting that
goal.

Related: rails/arel#130, ernie/squeel#153, ernie/squeel#156

Fix slightly broken Markdown syntax in actionpack/CHANGELOG.md

I think that 5 seconds was a bit low for our purposes.

Also enable it to be configured via env vars.

We also need to scale the number of records up/down depending on how
long we're running the benchmark for.

This means we can more easily compare numbers, and we don't have to
specify a single N for all reports, which previously meant that some
tests were running many more/fewer iterations than necessary.

For consistency with the other AR extension plugins we are creating.

AM::Validation#validates: custom exception for :strict option

Conflicts:
	activemodel/CHANGELOG.md

Since we removed the ActiveModel dependenxy from ActionPack at
166dbaa7 we don't need to require it
anymore.

Closes #7370

This was reverted in https://github.com/rails/rails/commit/fb883318c8b82b3570cee022ddf6886f9052245d

ActiveRecord::ConnectionAdapters::Column#microseconds did an unnecessary
conversion to from Rational to float when calculating the integer number
of microseconds. Some terminating decimal numbers in base10 are
repeating decimal numbers in base2 (the format of float), and
occasionally this causes a rounding error.
Patch & explanation originally from Logan Bowers.

Fix indentation on template errors to consider line number character count.

For instance, when an error is shown, if the related source code snippet has line numbers from, lets say, 8-12, the lines are left aligned, which means the code indent is wrong:

    8: foo
    9: bar
    10: raise
    11: baz
    12: ...

This changes it to right align the source code snippet, so that the indentation is correct:

     8: foo
     9: bar
    10: raise
    11: baz
    12: ...

Change Relation#update_all with blank argument to raise an ArgumentError 
instead of trying an update with empty fields.

No longer require AS::TestCase