Optimize internal extract! calls to save on memory allocation

[moberegger]

Simply optimizes internal calls to extract! to avoid extra memory allocations to splat the *attributes. Both _extract_hash_values and _extract_method_values accept an array for attributes, so no need to re-splat it by calling extract!, which then splats it again.

Solution is to implement a private _extract that just accepts an array, which can be used internally.

A simple way to compare it is with the call DSL, which was just running extract! underneath.

# person = { first_name: 'John', last_name: 'Doe', age: 30, city: 'New York' }

json.(person, :first_name, :last_name, :age, :city)

Warming up --------------------------------------
              before   156.678k i/100ms
               after   176.882k i/100ms
Calculating -------------------------------------
              before      1.674M (± 1.6%) i/s  (597.37 ns/i) -      8.461M in   5.055454s
               after      1.802M (± 2.0%) i/s  (554.82 ns/i) -      9.021M in   5.007138s

Comparison:
               after:  1802399.6 i/s
              before:  1673994.1 i/s - 1.08x  slower

Calculating -------------------------------------
              before   320.000  memsize (     0.000  retained)
                         6.000  objects (     0.000  retained)
                         4.000  strings (     0.000  retained)
               after   240.000  memsize (     0.000  retained)
                         5.000  objects (     0.000  retained)
                         4.000  strings (     0.000  retained)

Comparison:
               after:        240 allocated
              before:        320 allocated - 1.33x more

This change has no impact in using json.extract! directly.

# person = { first_name: 'John', last_name: 'Doe', age: 30, city: 'New York' }

json.extract! person, :first_name, :last_name, :age, :city

Calculating -------------------------------------
              before   240.000  memsize (     0.000  retained)
                         5.000  objects (     0.000  retained)
                         4.000  strings (     0.000  retained)
               after   240.000  memsize (     0.000  retained)
                         5.000  objects (     0.000  retained)
                         4.000  strings (     0.000  retained)

Comparison:
              before:        240 allocated
               after:        240 allocated - same