Replace fmt.Sprint with faster alternatives

[alexandear]

The PR replaces fmt.Sprint.* statements with faster alternatives suggested by the perfsprint linter:

• Replace fmt.Sprint(v) with strconv.FormatInt(v, 10), where v is int64.
• Replace fmt.Sprint(v) with strconv.FormatUint(v, 10), where v is uint64.
• Replace fmt.Sprint(v) with strconv.FormatBool(v), where v is bool.
• Replace fmt.Errorf(msg) with errors.New(msg).

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.00%. Comparing base (01f4bac) to head (c0f4ed5).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #555   +/-   ##
=======================================
  Coverage   77.00%   77.00%           
=======================================
  Files          21       21           
  Lines        7270     7270           
=======================================
  Hits         5598     5598           
  Misses       1277     1277           
  Partials      395      395           

[goccy]

Thank you for your contribution. This PR looks good. However, please note that I prefer to enable linters or perform refactoring at my own timing, so basically I do not plan to accept like these changes the next time. Thank you for your understanding.