Enable histogram

[jo-mueller]

Fixes #383

This re-enables the histogram functionality from the old clusters-plotter for the upcoming 0.9.0.

Long description

This pull request introduces enhancements to the napari_clusters_plotter plugin, focusing on adding support for 2D histograms, improving colormap handling, and refining the overall plotting functionality. It also includes updates to dependencies and new tests to ensure the robustness of the changes.

Feature Enhancements:

• Added support for 2D histograms by introducing a new plotting type HISTOGRAM2D and updating the PlottingType enum and related UI elements (_setup_ui, _on_plot_type_changed). [1] [2] [3]
• Introduced a colormap_reference dictionary to centralize colormap selection logic based on plot type and data categorization, simplifying the _replot method. [1] [2]

Dependency Updates:

• Updated the biaplotter dependency version from >=0.1.0 to >=0.2.0 in pyproject.toml.

Code Simplifications:

• Simplified colormap and color index handling in _color_layer_by_value by replacing multiple calls with a single color_indices_to_rgba method.
• Removed unused imports (ArtistType) and refactored active artist initialization to use string identifiers instead of enum members. [1] [2]

Testing Improvements:

• Added a new parameterized test test_histogram_support to validate the functionality of the new HISTOGRAM2D plot type with various layer types.

UI Updates:

• Enabled the plot_type_box dropdown in the UI to allow users to switch between plot types dynamically.