pass arel to select_all rather than depend on method_missing
fix visibility of the relation construction methods
Remove unnecessary string interpolation

Removed from controller template of scaffold generator.
Merge pull request #11385 from MarceloCajueiro/remove_string_interpolation

Remove unnecessary string interpolation
Avoid creating an extra Range instance
Speedup String#to

Benchmark:
1000000.times { str.to(30) }
          user     system      total        real
old   0.490000   0.110000   0.600000 (  0.607374)
new   0.390000   0.000000   0.390000 (  0.387306)
Speedup AS::Inflector.deconstantize

Benchmark:
          user     system      total        real
old   0.740000   0.000000   0.740000 (  0.744358)
new   0.550000   0.000000   0.550000 (  0.553690)
Speedup AS::Inflector.camelize

Benchmark:
          user     system      total        real
old   5.960000   0.020000   5.980000 (  5.981754)
new   5.740000   0.030000   5.770000 (  5.757201)