Replace references to lineages/variants with more generic vocabulary

[anwarMZ]

Given that we now have different ways of grouping data, time, location, wastewater, and lineages we should change the label "select lineages" to a more generic label. Something like "select/unselect" or select group"

[ivansg44]

There are also references to lineages in the help box, and the axis label "Variants".

Furthermore, there are references to lineages throughout the codebase. Need to think of a consistent generic vocabulary, and apply.