False negative for Performance/StringIdentifierArgument with string interpolation

[Earlopain]

As per rubocop/rubocop#12383 (comment) in the same vein as rubocop/rubocop#12373

Benchmark script:

require 'benchmark/ips'

puts `ruby -v`

def foo_bar
end

bar = "bar"

Benchmark.ips do |x|
  x.report('symbol arg') { send(:"foo_#{bar}") }
  x.report('string arg') { send("foo_#{bar}") }

  x.compare!
end

ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux-musl]
Warming up --------------------------------------
          symbol arg   641.253k i/100ms
          string arg   602.373k i/100ms
Calculating -------------------------------------
          symbol arg      6.385M (± 0.6%) i/s -     32.063M in   5.022123s
          string arg      6.023M (± 0.5%) i/s -     30.119M in   5.000717s

Comparison:
          symbol arg:  6384545.4 i/s
          string arg:  6023007.5 i/s - 1.06x  slower