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.

[petrasovaa]

The test functions can be executed in undefined order, so in the setUpClass you create the initial inputs, but the individual test functions modify them, so make sure that's not going to be a problem.