Modify the SNPObject to store LAI data at the SNP-level + add mehod to go from window-level to SNP-level in the WindowLevelAncestryObject

[miriambt]

SNPObject

• Added calldata_lai and ancestry_map to SNPObject for ancestry representation at the SNP level.
• Updated n_samples and n_snps to retrieve information from any available attribute.
• Introduced n_ancestries to obtain the number of ancestries when calldata_lai is present.
• Extended filter_samples and filter_snps to also filter calldata_lai if available.

LocalAncestryObject

• Renamed LocalAncestryObject to WindowLevelAncestryObject.
• Added convert_to_snp_level method to transform a WindowLevelAncestryObject into an SNP-level SNPObject. This method uniformly generates SNPs across genomic window boundaries and also supports assigning ancestry values to specified SNP coordinates.

MSPReader

• Fixed a bug in MSPReader by ensuring chromosome values are converted to strings.