Add default MAX_RAND value for length 16 & 32

[tungmq]

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Overview

• I ran two cases:
  The first one is for default values that we're using in codebase (length 16 & 32).
  The second one is custom length (value: 15).

• Benchmark result

Benchmark.ips do |x|
  x.report("generate_guid") {
    generate_guid
  }
  x.report("generate_guid_new") {
    generate_guid_new
  }
  x.compare!
end
----------------------------------------------------------------------------
Warming up --------------------------------------
       generate_guid   300.331k i/100ms
   generate_guid_new   394.048k i/100ms
Calculating -------------------------------------
       generate_guid      3.005M (± 0.1%) i/s -     15.317M in   5.097986s
   generate_guid_new      3.944M (± 0.4%) i/s -     20.096M in   5.095270s

Comparison:
   generate_guid_new:  3944187.7 i/s
       generate_guid:  3004503.1 i/s - 1.31x  (± 0.00) slower

Benchmark.ips do |x|
  x.report("generate_guid with custom length") {
    generate_guid(15)
  }
  x.report("generate_guid_new with custom length") {
    generate_guid_new(15)
  }
  x.compare!
end
----------------------------------------------------------------------------
Warming up --------------------------------------
generate_guid with custom length
                       574.869k i/100ms
generate_guid_new with custom length
                       541.947k i/100ms
Calculating -------------------------------------
generate_guid with custom length
                          5.731M (± 0.5%) i/s -     28.743M in   5.015260s
generate_guid_new with custom length
                          5.414M (± 0.2%) i/s -     27.097M in   5.005517s

Comparison:
generate_guid with custom length:  5731344.7 i/s
generate_guid_new with custom length:  5413515.2 i/s - 1.06x  (± 0.00) slower

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• Include a link to the related GitHub issue, if applicable
• Include a security review link, if applicable

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Reviewer Checklist

• Perform code review
• Add performance label
• Perform appropriate level of performance testing
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[CLAassistant]

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[hannahramadan]

Hi tungmq! This looks great and we appreciate the performance benchmarks you shared. I made a small formatting edit to make our linter happy. Thank you for your contribution!

[fallwith]

Hi @tungmq. Thanks for the performance boost! This change has gone out in v8.14.0 of the newrelic_rpm gem and you have been recognized as a contributor in our CHANGELOG!