i.biomass: added test file for i.biomass module

[jayneel-shah18]

This PR introduces a suite of tests for the i.biomass GRASS GIS module, covering a range of scenarios, including functionality validation, property testing, edge cases, and performance evaluation.

Key updates in this PR include:

• Functionality: Verify output raster existence and dimensions.
• Properties: Test linearity and latitude dependency.
• Edge Cases: Validate behavior with zero and extreme input values.
• Performance: Test large-scale processing.

Test Case Additions:

• Basic Functionality:

  • Validate the creation and existence of the biomass output raster.

• Advanced Properties:

  • Linearity: Verify output scales proportionally with input.
  • Latitude Dependency: Ensure biomass values vary reasonably with latitude.

• Edge Cases:

  • Handle all-zero input rasters.
  • Test extreme values for all parameters.

• Performance:

  • Assess processing of large input rasters.