New ANC indicators 2022

[jeffeaton]

This PR updates the ANC example data for new fields in 2023: anc_known_neg, births_facility.

• Bump version number to 2.7.0 -- for UNAIDS 2023 related updates.
• Update example data sets with new indicator fields
• Update read_anc_testing() to parse data set with additional fields.
  • For backwards compatibility, if anc_known_neg field is missing or is all NA values, it is replaced by a column of 0s.
• Update calculate_anc_prevalence() to add anc_known_neg to denominator.
• Update anc_testing_prev_mf() to add anc_known_neg to denominator.

TO DO (@rtesra):

• [x] Update input time-series plot code for anc_known_neg. Should be completed before merging this PR.
• [ ] Add input time series plot comparing anc_clients vs. births_facility. Does not need to be completed before merging this PR; can push to an issue for future attention.

[vimc-robot]

Thanks. Corresponding hintr PR at https://github.com/mrc-ide/hintr/pull/395

[jeffeaton]

This looks good, do we want this to be plotted on input data? At the moment ANC input data plots "ANC HIV prevalence" and "ANC prior HIV ART coverage". These columns are computed from the input data. Just wanted to check do we want to plot any other data? If not then this PR looks good to merge

Eventually yes—we want to plot births_facility relative to anc_clients. Have suggested to @rtesra to make a separate ticket for that as it can be independent from this PR.