Inherit SpaceMarkers object from SpatialExperiment and add wrapper compatibility functions

[atuldeshpande]

Feature Request

Objective:

• Refactor the SpaceMarkers package to have its main object (SpaceMarkers) inherit from the SpatialExperiment class.
• Develop wrapper functions so that all existing SpaceMarkers functions are compatible with the new object design.

Rationale

• Inheritance from SpatialExperiment will allow seamless interoperability with existing Bioconductor spatial packages and their functions.
• Wrapper methods will reduce code duplication and simplify maintenance while ensuring backward compatibility for users relying on current functions.

Suggested Steps

1. Define the SpaceMarkers object to inherit from SpatialExperiment.
2. Identify all functions involved in the SpaceMarkers analysis.
3. Write wrapper functions to map input/output and methods for compatibility.
4. Update documentation/examples to reflect these changes.
5. Add unit tests to check compatibility and functionality.

Acceptance Criteria

• SpaceMarkers successfully inherits from SpatialExperiment.
• All current package functions work as expected when passed a SpaceMarkers object.
• Documentation and tests are up-to-date.