Fix rubocop offenses

[yhirano55]

This pull request includes various changes to improve code quality, fix RuboCop offenses, and enhance the trace_location gem. The most important changes include updating the RuboCop configuration, modifying error handling, and improving test descriptions and structure.

RuboCop Configuration Updates:

• Removed exclusions for several RuboCop cops in the .rubocop_todo.yml file. This change ensures that the codebase adheres to more stringent linting rules.

Code Quality Improvements:

• Added # frozen_string_literal: true to several files to optimize string handling and improve performance. [1] [2]
• Replaced $stderr.puts with warn for better error handling and consistency in lib/trace_location.rb.
• Updated eval usage to include a RuboCop directive to disable the security warning in lib/trace_location/cli.rb.

Testing Enhancements:

• Improved test descriptions and structure in spec/trace_location_spec.rb by using described_class and adding context blocks for better readability and maintainability. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

Documentation and Changelog:

• Updated the CHANGELOG.md to include a note about fixing RuboCop offenses.
• Improved the gem description formatting in trace_location.gemspec for better readability.

These changes collectively enhance the code quality, maintainability, and performance of the trace_location gem.