build: add stricter compilation warnings for improved code quality

[Copilot]

Summary

This PR implements comprehensive compiler warning flags to improve code quality and catch potential issues during compilation. The warnings are configured in the library's build script and will apply to both the library code and projects that depend on it.

Changes Made

Added the following warning flags to scripts/setup_library_env.py:

Core Warning Sets

• -Wall - Enables all standard warnings
• -Wextra - Enables additional warnings beyond -Wall

Unused Code Detection

• -Wunused - Umbrella warning for all unused code
• -Wunused-variable - Catches unused local variables
• -Wunused-parameter - Detects unused function parameters
• -Wunused-function - Identifies unused static functions

Code Quality & Safety

• -Wshadow - Warns about variable shadowing
• -Wuninitialized - Detects potentially uninitialized variables
• -Wmissing-field-initializers - Ensures complete struct/class initialization
• -Wformat=2 - Enhanced format string validation for printf-style functions

Benefits

• Early Issue Detection: Catch bugs and code quality issues at compile time
• Developer Feedback: Immediate warnings about unused variables, uninitialized data, and format errors
• Consistent Standards: Applied uniformly across all build environments (ESP32, ESP8266, library, and examples)
• Maintainability: Encourages cleaner, more maintainable code

Impact

These warnings will help developers identify:

• Dead code that can be removed
• Potential uninitialized variable bugs
• Variable shadowing that could cause confusion
• Format string vulnerabilities
• Missing struct member initializations

The changes are backward compatible and non-breaking. Projects using this library will benefit from these warnings during their builds, helping catch issues earlier in the development cycle.

Original prompt

Implement stricter compilation warnings like warning for unused variables. Suggest in your initial plan and then allow me to accept

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