Improve the performance of `ActiveSupport::Inflector.ordinal`

This improves the performance for the most ordinalized numbers (1st,
2nd, 3rd, etc).

```
require "benchmark/ips"

def o1(number)
  abs_number = number.to_i.abs

  if (11..13).include?(abs_number % 100)
    "th"
  else
    case abs_number % 10
    when 1; "st"
    when 2; "nd"
    when 3; "rd"
    else    "th"
    end
  end
end

def o3(number)
  case number
  when 1; "st"
  when 2; "nd"
  when 3; "rd"
  when 4, 5, 6, 7, 8, 9, 10, 11, 12, 13; "th"
  else
    num_modulo = number.to_i.abs % 100
    if 11 <= num_modulo && num_modulo <= 13
      "th"
    else
      case num_modulo % 10
      when 1; "st"
      when 2; "nd"
      when 3; "rd"
      else    "th"
      end
    end
  end
end

def o4(number)
  case number
  when 1; "st"
  when 2; "nd"
  when 3; "rd"
  when 4, 5, 6, 7, 8, 9, 10, 11, 12, 13; "th"
  else
    num_modulo = number.to_i.abs % 100
    num_modulo %= 10 if num_modulo > 13
    case num_modulo
    when 1; "st"
    when 2; "nd"
    when 3; "rd"
    else    "th"
    end
  end
end

puts RUBY_DESCRIPTION
Benchmark.ips do |x|
  x.report("orig") { o1(1); o1(2); o1(3); o1(4); o1(11); o1(111); o1(1523) }
  x.report("ord3") { o3(1); o3(2); o3(3); o3(4); o3(11); o3(111); o3(1523) }
  x.report("ord4") { o4(1); o4(2); o4(3); o4(4); o4(11); o4(111); o4(1523) }
  x.compare!
end
```

```
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin15]
Warming up --------------------------------------
                orig    25.305k i/100ms
                ord3   121.146k i/100ms
                ord4   124.944k i/100ms
Calculating -------------------------------------
                orig    275.496k (± 2.4%) i/s -      1.392M in   5.054720s
                ord3      1.649M (± 5.0%) i/s -      8.238M in   5.009801s
                ord4      1.700M (± 7.0%) i/s -      8.496M in   5.031646s

Comparison:
                ord4:  1700059.6 i/s
                ord3:  1649154.9 i/s - same-ish: difference falls within error
                orig:   275496.3 i/s - 6.17x  slower
```

Closes #25020.

[lvl0nax, Jeremy Daer, Ryuta Kamizono]

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