Consolidate issues into one dataframe

[apriha]

Building on #107, consolidate several issues (e.g., duplicate_rsid, discrepant_XY) into one dataframe with the following columns / dtypes:

Column	pandas dtype
rsid	pd.StringDtype()
chrom	pd.CategoricalDtype()
pos	pd.UInt32Dtype()
genotype	pd.CategoricalDtype()
duplicate_rsid	pd.BooleanDtype()
discrepant_loci	pd.BooleanDtype()
discrepant_XY	pd.BooleanDtype()
heterozygous_MT	pd.BooleanDtype()
discrepant_vcf_position	pd.BooleanDtype()
discrepant_merge_position	pd.BooleanDtype()
discrepant_merge_genotype	pd.BooleanDtype()

Multiple issue columns could take on the value of True, and getting SNPs with issues (e.g., discrepant_XY) could be handled by filtering the issues dataframe.

rsids could appear more than once in this dataframe. However, if an rsid has two or more rows that are equivalent (same values for chrom, pos, and genotype), their issues should be consolidated into one row, with the issue columns flagging the issue(s).