Refactor Wrapper API, Migrate to RST Docs, and Switch to Pixi

[AntonioCC808]

Merge Request: Refactor Wrapper API, Migrate to RST Docs, and Switch to Pixi

Description:

This PR implements a major overhaul of the earthkit-climate wrapper architecture, migrates the project tooling to pixi, converts documentation to reStructuredText, and significantly enhances the test suite and performance analysis tools.

Detailed Changes:

• API & Wrapper Architecture:

  • Created api package: restructured the codebase to centralize wrapper logic.
  • Simplified Signatures: Refactored indicator functions to accept a single earthkit.data object (renamed to ds) instead of multiple variable arguments, improving consistency.
  • Unit Handling: Standardized temperature units to degC and integrated xclim unit conversions directly.

• Documentation:

  • Format Migration: Converted all documentation from Markdown to reStructuredText (RST) for robust Sphinx support.
  • Content Updates: Enhanced index.rst with detailed integration guides, added project structure descriptions, and included a new SVG logo.
  • Notebooks: Added and refined docs/notebooks/performance_analysis.ipynb with system info, memory profiling, and comparative analysis.

• Tooling & Dev Experience:

  • Pixi Migration: Replaced the Makefile workflow with pixi for dependency management and task execution.
  • Updated pyproject.toml and pixi.lock dependencies.

• New Features:

  • Percentile Utilities: Added utilities for percentile calculations and refactored indices (like WSDI) to accept pre-calculated thresholds.
  • Performance Monitoring: Added memory profiling and system information cells to performance notebooks.

• Testing:

  • Replaced generic integration tests with dedicated unit tests for precipitation and temperature indicators.
  • Fixed ModuleNotFoundError and mocking issues in the test suite.