Feature/omics layers

[DanielGarbozo]

This pull request introduces new circos plot functionality and improves the robustness and usability of the nice_GenomeTrack function. The most significant changes are the addition of new functions for genome-wide circos plotting, improved input validation and error handling for annotation data, and updated package dependencies and documentation.

New circos plot functionality:

• Added the nice_circos function for plotting genome-wide circos tracks for multi-omics data, with comprehensive documentation and support for multiple data types, metadata rings, and genomic links.
• Introduced the resolve_genome function to standardize cytoband and chromosome order for circos plots, with a new S3 class circos_genome and corresponding documentation.
• Added the is_circos_genome function to test for circos genome descriptors, and an S3 print method for circos_genome objects, both with documentation. [1] [2]
• Exported the new circos-related functions and methods in the NAMESPACE. [1] [2] [3]

Improvements to nice_GenomeTrack:

• Improved input validation for local annotation data, ensuring required columns are present before any BioMart connection is attempted. [1] [2]
• Deferred BioMart connection and dependency checks until needed (i.e., only when annotations are not provided or show_transcripts = TRUE), with clearer error messages. [1] [2] [3]
• Ensured transcript tracks require a valid BioMart connection and fail gracefully if unavailable.

Package dependencies and testing:

• Updated DESCRIPTION to add grDevices and tools to Imports, and moved grDevices to Imports from Suggests. Added mockery to Suggests. [1] [2]
• Updated NAMESPACE to import new functions from grDevices, grid, and tools.
• Improved tests for nice_GenomeTrack to work without requiring BioMart, and added checks for output files. [1] [2]