Logger middleware json string escaping and deprecation

[aldas]

Security

• Logger middleware: escape string values when logger format looks like JSON. See middleware/DefaultLoggerConfig looks like JSON, but doesn't escape #2846

Enhancements

• Add middleware.RequestLogger function to replace middleware.Logger. middleware.RequestLogger uses default slog logger.
  Default slog logger output can be configured to JSON format like that:

  slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, nil)))
  e.Use(middleware.RequestLogger())

• Deprecate middleware.Logger function and point users to middleware.RequestLogger and middleware.RequestLoggerWithConfig

[codecov]

Codecov Report

❌ Patch coverage is 85.43046% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.91%. Comparing base (f24aaff) to head (7a19984).
⚠️ Report is 21 commits behind head on master.

Files with missing lines	Patch %	Lines
middleware/logger_strings.go	71.42%	10 Missing and 10 partials ⚠️
middleware/request_logger.go	96.29%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2849      +/-   ##
==========================================
+ Coverage   93.25%   93.91%   +0.66%     
==========================================
  Files          39       40       +1     
  Lines        4652     3946     -706     
==========================================
- Hits         4338     3706     -632     
+ Misses        218      137      -81     
- Partials       96      103       +7     

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[aldas]

@vishr I have added logger_strings.go file with this PR that contains (modified) code from Go standard library and that file has their license (BSD-3-Clause). Is this fine with you?